[melted] / src / modules / avformat / producer_avformat.c

/*
 * producer_avformat.c -- avformat producer
 * Copyright (C) 2003-2004 Ushodaya Enterprises Limited
 * Author: Charles Yates <charles.yates@pandora.be>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

// Local header files
#include "producer_avformat.h"

// MLT Header files
#include <framework/mlt_frame.h>

// ffmpeg Header files
#include <ffmpeg/avformat.h>

// System header files
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <math.h>

// Forward references.
static int producer_open( mlt_producer this, char *file );
static int producer_get_frame( mlt_producer this, mlt_frame_ptr frame, int index );

// A static flag used to determine if avformat has been initialised
static int avformat_initialised = 0;
static pthread_mutex_t avformat_mutex;

/** Constructor for libavformat.
*/

mlt_producer producer_avformat_init( char *file )
{
        mlt_producer this = NULL;

        // Check that we have a non-NULL argument
        if ( file != NULL )
        {
                // Construct the producer
                this = calloc( 1, sizeof( struct mlt_producer_s ) );

                // Initialise it
                if ( mlt_producer_init( this, NULL ) == 0 )
                {
                        // Get the properties
                        mlt_properties properties = mlt_producer_properties( this );

                        // Set the resource property (required for all producers)
                        mlt_properties_set( properties, "resource", file );

                        // TEST: audio sync tweaking
                        mlt_properties_set_double( properties, "discrepancy", 1 );

                        // Register our get_frame implementation
                        this->get_frame = producer_get_frame;

                        // Initialise avformat if necessary
                        if ( avformat_initialised == 0 )
                        {
                                pthread_mutex_init( &avformat_mutex, NULL );
                                avformat_initialised = 1;
                                av_register_all( );
                        }

                        // Open the file
                        if ( producer_open( this, file ) != 0 )
                        {
                                // Clean up
                                mlt_producer_close( this );
                                this = NULL;
                        }
                }
        }

        return this;
}

/** Find the default streams.
*/

static void find_default_streams( AVFormatContext *context, int *audio_index, int *video_index )
{
        int i;

        // Allow for multiple audio and video streams in the file and select first of each (if available)
        for( i = 0; i < context->nb_streams; i++ ) 
        {
                // Get the codec context
                AVCodecContext *codec_context = &context->streams[ i ]->codec;

                // Determine the type and obtain the first index of each type
                switch( codec_context->codec_type ) 
                {
                        case CODEC_TYPE_VIDEO:
                                if ( *video_index < 0 )
                                        *video_index = i;
                                break;
                        case CODEC_TYPE_AUDIO:
                                if ( *audio_index < 0 )
                                        *audio_index = i;
                                break;
                        default:
                                break;
                }
        }
}

/** Producer file destructor.
*/

static void producer_file_close( void *context )
{
        if ( context != NULL )
        {
                // Lock the mutex now
                pthread_mutex_lock( &avformat_mutex );

                // Close the file
                av_close_input_file( context );

                // Unlock the mutex now
                pthread_mutex_unlock( &avformat_mutex );
        }
}

/** Producer file destructor.
*/

static void producer_codec_close( void *codec )
{
        if ( codec != NULL )
        {
                // Lock the mutex now
                pthread_mutex_lock( &avformat_mutex );

                // Close the file
                avcodec_close( codec );

                // Unlock the mutex now
                pthread_mutex_unlock( &avformat_mutex );
        }
}

/** Open the file.
*/

static int producer_open( mlt_producer this, char *file )
{
        // Return an error code (0 == no error)
        int error = 0;

        // Context for avformat
        AVFormatContext *context = NULL;

        // Get the properties
        mlt_properties properties = mlt_producer_properties( this );

        // We will treat everything with the producer fps
        double fps = mlt_properties_get_double( properties, "fps" );

        // Lock the mutex now
        pthread_mutex_lock( &avformat_mutex );

        // Now attempt to open the file
        error = av_open_input_file( &context, file, NULL, 0, NULL );
        error = error < 0;

        // If successful, then try to get additional info
        if ( error == 0 )
        {
                // Get the stream info
                error = av_find_stream_info( context ) < 0;

                // Continue if no error
                if ( error == 0 )
                {
                        // We will default to the first audio and video streams found
                        int audio_index = -1;
                        int video_index = -1;

                        // Now set properties where we can (use default unknowns if required)
                        if ( context->duration != AV_NOPTS_VALUE ) 
                        {
                                // This isn't going to be accurate for all formats
                                mlt_position frames = ( mlt_position )( ( ( double )context->duration / ( double )AV_TIME_BASE ) * fps );
                                mlt_properties_set_position( properties, "out", frames - 2 );
                                mlt_properties_set_position( properties, "length", frames - 1 );
                        }

                        // Find default audio and video streams
                        find_default_streams( context, &audio_index, &video_index );

                        // Store selected audio and video indexes on properties
                        mlt_properties_set_int( properties, "audio_index", audio_index );
                        mlt_properties_set_int( properties, "video_index", video_index );

                        // We're going to cheat here - for a/v files, we will have two contexts (reasoning will be clear later)
                        if ( audio_index != -1 && video_index != -1 )
                        {
                                // We'll use the open one as our video_context
                                mlt_properties_set_data( properties, "video_context", context, 0, producer_file_close, NULL );

                                // And open again for our audio context
                                av_open_input_file( &context, file, NULL, 0, NULL );
                                av_find_stream_info( context );

                                // Audio context
                                mlt_properties_set_data( properties, "audio_context", context, 0, producer_file_close, NULL );
                        }
                        else if ( video_index != -1 )
                        {
                                // We only have a video context
                                mlt_properties_set_data( properties, "video_context", context, 0, producer_file_close, NULL );
                        }
                        else if ( audio_index != -1 )
                        {
                                // We only have an audio context
                                mlt_properties_set_data( properties, "audio_context", context, 0, producer_file_close, NULL );
                        }
                        else
                        {
                                // Something has gone wrong
                                error = -1;
                        }
                }
        }

        // Unlock the mutex now
        pthread_mutex_unlock( &avformat_mutex );

        return error;
}

/** Convert a frame position to a time code.
*/

static double producer_time_of_frame( mlt_producer this, mlt_position position )
{
        // Get the properties
        mlt_properties properties = mlt_producer_properties( this );

        // Obtain the fps
        double fps = mlt_properties_get_double( properties, "fps" );

        // Do the calc
        return ( double )position / fps;
}

/** Get an image from a frame.
*/

static int producer_get_image( mlt_frame frame, uint8_t **buffer, mlt_image_format *format, int *width, int *height, int writable )
{
        // Get the properties from the frame
        mlt_properties frame_properties = mlt_frame_properties( frame );

        // Obtain the frame number of this frame
        mlt_position position = mlt_properties_get_position( frame_properties, "avformat_position" );

        // Get the producer 
        mlt_producer this = mlt_properties_get_data( frame_properties, "avformat_producer", NULL );

        // Get the producer properties
        mlt_properties properties = mlt_producer_properties( this );

        // Fetch the video_context
        AVFormatContext *context = mlt_properties_get_data( properties, "video_context", NULL );

        // Get the video_index
        int index = mlt_properties_get_int( properties, "video_index" );

        // Obtain the expected frame numer
        mlt_position expected = mlt_properties_get_position( properties, "video_expected" );

        // Calculate the real time code
        double real_timecode = producer_time_of_frame( this, position );

        // Get the video stream
        AVStream *stream = context->streams[ index ];

        // Get codec context
        AVCodecContext *codec_context = &stream->codec;

        // Packet
        AVPacket pkt;

        // Get the conversion frame
        AVPicture *output = mlt_properties_get_data( properties, "video_output_frame", NULL );

        // Special case pause handling flag
        int paused = 0;

        // Special case ffwd handling
        int ignore = 0;

        // Current time calcs
        double current_time = mlt_properties_get_double( properties, "current_time" );

        // We may want to use the source fps if available
        double source_fps = mlt_properties_get_double( properties, "source_fps" );

        // Set the result arguments that we know here (only *buffer is now required)
        *format = mlt_image_yuv422;
        *width = codec_context->width;
        *height = codec_context->height;

        // Set this on the frame properties
        mlt_properties_set_int( frame_properties, "width", *width );
        mlt_properties_set_int( frame_properties, "height", *height );

        // Lock the mutex now
        pthread_mutex_lock( &avformat_mutex );

        // Construct an AVFrame for YUV422 conversion
        if ( output == NULL )
        {
                int size = avpicture_get_size( PIX_FMT_YUV422, *width, *height );
                size += *width * 2;
                uint8_t *buf = mlt_pool_alloc( size );
                output = mlt_pool_alloc( sizeof( AVPicture ) );
                //memset( output, 0, sizeof( AVPicture ) );
                avpicture_fill( output, buf, PIX_FMT_YUV422, *width, *height );
                mlt_properties_set_data( properties, "video_output_frame", output, 0, ( mlt_destructor )mlt_pool_release, NULL );
                mlt_properties_set_data( properties, "video_output_buffer", buf, 0, ( mlt_destructor )mlt_pool_release, NULL );
        }

        // Seek if necessary
        if ( position != expected )
        {
                if ( position + 1 == expected )
                {
                        // We're paused - use last image
                        paused = 1;
                }
                else if ( position > expected && ( position - expected ) < 250 )
                {
                        // Fast forward - seeking is inefficient for small distances - just ignore following frames
                        ignore = position - expected;
                }
                else
                {
                        // Set to the real timecode
                        av_seek_frame( context, -1, real_timecode * 1000000.0 );
        
                        // Remove the cached info relating to the previous position
                        mlt_properties_set_double( properties, "current_time", real_timecode );
                        mlt_properties_set_data( properties, "current_image", NULL, 0, NULL, NULL );
                }
        }
        
        // Duplicate the last image if necessary
        if ( mlt_properties_get_data( properties, "current_image", NULL ) != NULL &&
                 ( paused || mlt_properties_get_double( properties, "current_time" ) >= real_timecode ) )
        {
                // Get current image and size
                int size = 0;
                uint8_t *image = mlt_properties_get_data( properties, "current_image", &size );

                // Duplicate it
                *buffer = mlt_pool_alloc( size );
                memcpy( *buffer, image, size );

                // Set this on the frame properties
                mlt_properties_set_data( frame_properties, "image", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );
        }
        else
        {
                int ret = 0;
                int got_picture = 0;
                AVFrame frame;

                memset( &pkt, 0, sizeof( pkt ) );
                memset( &frame, 0, sizeof( frame ) );

                while( ret >= 0 && !got_picture )
                {
                        // Read a packet
                        ret = av_read_frame( context, &pkt );

                        // We only deal with video from the selected video_index
                        if ( ret >= 0 && pkt.stream_index == index && pkt.size > 0 )
                        {
                                // Decode the image
                                ret = avcodec_decode_video( codec_context, &frame, &got_picture, pkt.data, pkt.size );

                                if ( got_picture )
                                {
                                        if ( pkt.pts != AV_NOPTS_VALUE && pkt.pts != 0  )
                                                current_time = ( double )pkt.pts / 1000000.0;
                                        else
                                                current_time = real_timecode;

                                        // Handle ignore
                                        if ( current_time < real_timecode )
                                        {
                                                ignore = 0;
                                                got_picture = 0;
                                        }
                                        else if ( current_time >= real_timecode )
                                        {
                                                //current_time = real_timecode;
                                                ignore = 0;
                                        }
                                        else if ( ignore -- )
                                        {
                                                got_picture = 0;
                                        }
                                }
                        }

                        // We're finished with this packet regardless
                        av_free_packet( &pkt );
                }

                // Now handle the picture if we have one
                if ( got_picture )
                {
                        // Get current image and size
                        int size = 0;
                        uint8_t *image = mlt_properties_get_data( properties, "current_image", &size );

                        if ( image == NULL || size != *width * *height * 2 )
                        {
                                size = *width * ( *height + 1 ) * 2;
                                image = mlt_pool_alloc( size );
                                mlt_properties_set_data( properties, "current_image", image, size, ( mlt_destructor )mlt_pool_release, NULL );
                        }

                        *buffer = mlt_pool_alloc( size );

                        // EXPERIMENTAL IMAGE NORMALISATIONS
                        if ( codec_context->pix_fmt == PIX_FMT_YUV420P )
                        {
                                register int i, j;
                                register int half = *width >> 1;
                                register uint8_t *Y = ( ( AVPicture * )&frame )->data[ 0 ];
                                register uint8_t *U = ( ( AVPicture * )&frame )->data[ 1 ];
                                register uint8_t *V = ( ( AVPicture * )&frame )->data[ 2 ];
                                register uint8_t *d = *buffer;
                                register uint8_t *y, *u, *v;

                                i = *height >> 1;
                                while ( i -- )
                                {
                                        y = Y;
                                        u = U;
                                        v = V;
                                        j = half;
                                        while ( j -- )
                                        {
                                                *d ++ = *y ++;
                                                *d ++ = *u ++;
                                                *d ++ = *y ++;
                                                *d ++ = *v ++;
                                        }

                                        Y += ( ( AVPicture * )&frame )->linesize[ 0 ];
                                        y = Y;
                                        u = U;
                                        v = V;
                                        j = half;
                                        while ( j -- )
                                        {
                                                *d ++ = *y ++;
                                                *d ++ = *u ++;
                                                *d ++ = *y ++;
                                                *d ++ = *v ++;
                                        }

                                        Y += ( ( AVPicture * )&frame )->linesize[ 0 ];
                                        U += ( ( AVPicture * )&frame )->linesize[ 1 ];
                                        V += ( ( AVPicture * )&frame )->linesize[ 2 ];
                                }
                        }
                        else
                        {
                                img_convert( output, PIX_FMT_YUV422, (AVPicture *)&frame, codec_context->pix_fmt, *width, *height );
                                memcpy( *buffer, output->data[ 0 ], size );
                        }

                        memcpy( image, *buffer, size );
                        mlt_properties_set_data( frame_properties, "image", *buffer, size, ( mlt_destructor )mlt_pool_release, NULL );

                        if ( current_time == 0 && source_fps != 0 )
                        {
                                double fps = mlt_properties_get_double( properties, "fps" );
                                current_time = ceil( source_fps * ( double )position / fps ) * ( 1 / source_fps );
                                mlt_properties_set_double( properties, "current_time", current_time );
                        }
                        else
                        {
                                mlt_properties_set_double( properties, "current_time", current_time );
                        }
                }
        }

        // Regardless of speed, we expect to get the next frame (cos we ain't too bright)
        mlt_properties_set_position( properties, "video_expected", position + 1 );

        // Unlock the mutex now
        pthread_mutex_unlock( &avformat_mutex );

        return 0;
}

/** Set up video handling.
*/

static void producer_set_up_video( mlt_producer this, mlt_frame frame )
{
        // Get the properties
        mlt_properties properties = mlt_producer_properties( this );

        // Fetch the video_context
        AVFormatContext *context = mlt_properties_get_data( properties, "video_context", NULL );

        // Get the video_index
        int index = mlt_properties_get_int( properties, "video_index" );

        // Get the frame properties
        mlt_properties frame_properties = mlt_frame_properties( frame );

        // Lock the mutex now
        pthread_mutex_lock( &avformat_mutex );

        if ( context != NULL && index != -1 )
        {
                // Get the video stream
                AVStream *stream = context->streams[ index ];

                // Get codec context
                AVCodecContext *codec_context = &stream->codec;

                // Get the codec
                AVCodec *codec = mlt_properties_get_data( properties, "video_codec", NULL );

                // Initialise the codec if necessary
                if ( codec == NULL )
                {
                        // Find the codec
                        codec = avcodec_find_decoder( codec_context->codec_id );

                        // If we don't have a codec and we can't initialise it, we can't do much more...
                        if ( codec != NULL && avcodec_open( codec_context, codec ) >= 0 )
                        {
                                double aspect_ratio = 0;
                                double source_fps = 0;

                                // Set aspect ratio
                                if ( codec_context->sample_aspect_ratio.num == 0 ) 
                                        aspect_ratio = 0;
                                else
                                        aspect_ratio = av_q2d( codec_context->sample_aspect_ratio ) * codec_context->width / codec_context->height;

                                // XXX: This assumes square pixels!
                        if (aspect_ratio <= 0.0)
                                        aspect_ratio = ( double )codec_context->width / ( double )codec_context->height;

                                mlt_properties_set_double( properties, "aspect_ratio", aspect_ratio );
                                fprintf( stderr, "AVFORMAT: sample aspect %f computed display aspect %f\n", av_q2d( codec_context->sample_aspect_ratio ), aspect_ratio );

                                // Determine the fps
                                source_fps = ( double )codec_context->frame_rate / codec_context->frame_rate_base;

                                // We'll use fps if it's available
                                if ( source_fps > 0 && source_fps < 30 )
                                        mlt_properties_set_double( properties, "source_fps", source_fps );

                                // Now store the codec with its destructor
                                mlt_properties_set_data( properties, "video_codec", codec_context, 0, producer_codec_close, NULL );
                        }
                        else
                        {
                                // Remember that we can't use this later
                                mlt_properties_set_int( properties, "video_index", -1 );
                        }
                }

                // No codec, no show...
                if ( codec != NULL )
                {
                        mlt_frame_push_get_image( frame, producer_get_image );
                        mlt_properties_set_data( frame_properties, "avformat_producer", this, 0, NULL, NULL );
                }
                else
                {
                        mlt_properties_set_int( frame_properties, "test_image", 1 );
                }
        }
        else
        {
                mlt_properties_set_int( frame_properties, "test_image", 1 );
        }

        // Unlock the mutex now
        pthread_mutex_unlock( &avformat_mutex );
}

/** Get the audio from a frame.
*/

static int producer_get_audio( mlt_frame frame, int16_t **buffer, mlt_audio_format *format, int *frequency, int *channels, int *samples )
{
        // Get the properties from the frame
        mlt_properties frame_properties = mlt_frame_properties( frame );

        // Obtain the frame number of this frame
        mlt_position position = mlt_properties_get_position( frame_properties, "avformat_position" );

        // Get the producer 
        mlt_producer this = mlt_properties_get_data( frame_properties, "avformat_producer", NULL );

        // Get the producer properties
        mlt_properties properties = mlt_producer_properties( this );

        // Fetch the audio_context
        AVFormatContext *context = mlt_properties_get_data( properties, "audio_context", NULL );

        // Get the audio_index
        int index = mlt_properties_get_int( properties, "audio_index" );

        // Obtain the expected frame numer
        mlt_position expected = mlt_properties_get_position( properties, "audio_expected" );

        // Obtain the resample context if it exists (not always needed)
        ReSampleContext *resample = mlt_properties_get_data( properties, "audio_resample", NULL );

        // Obtain the audio buffer
        int16_t *audio_buffer = mlt_properties_get_data( properties, "audio_buffer", NULL );

        // Get amount of audio used
        int audio_used =  mlt_properties_get_int( properties, "audio_used" );

        // Calculate the real time code
        double real_timecode = producer_time_of_frame( this, position );

        // Get the audio stream
        AVStream *stream = context->streams[ index ];

        // Get codec context
        AVCodecContext *codec_context = &stream->codec;

        // Packet
        AVPacket pkt;

        // Number of frames to ignore (for ffwd)
        int ignore = 0;

        // Flag for paused (silence) 
        int paused = 0;
        int locked = 0;

        // Lock the mutex now
        pthread_mutex_lock( &avformat_mutex );

        // Check for resample and create if necessary
        if ( resample == NULL )
        {
                // Create the resampler
                resample = audio_resample_init( *channels, codec_context->channels, *frequency, codec_context->sample_rate );

                // And store it on properties
                mlt_properties_set_data( properties, "audio_resample", resample, 0, ( mlt_destructor )audio_resample_close, NULL );
        }

        // Check for audio buffer and create if necessary
        if ( audio_buffer == NULL )
        {
                // Allocate the audio buffer
                audio_buffer = mlt_pool_alloc( AVCODEC_MAX_AUDIO_FRAME_SIZE * sizeof( int16_t ) );

                // And store it on properties for reuse
                mlt_properties_set_data( properties, "audio_buffer", audio_buffer, 0, ( mlt_destructor )mlt_pool_release, NULL );
        }

        // Seek if necessary
        if ( position != expected )
        {
                if ( position + 1 == expected )
                {
                        // We're paused - silence required
                        paused = 1;
                }
                else if ( position > expected && ( position - expected ) < 250 )
                {
                        // Fast forward - seeking is inefficient for small distances - just ignore following frames
                        ignore = position - expected;
                }
                else
                {
                        // Set to the real timecode
                        av_seek_frame( context, -1, real_timecode * 1000000.0 );

                        // Clear the usage in the audio buffer
                        audio_used = 0;

                        locked = 1;
                }
        }

        // Get the audio if required
        if ( !paused )
        {
                int ret = 0;
                int got_audio = 0;
                int16_t *temp = mlt_pool_alloc( sizeof( int16_t ) * AVCODEC_MAX_AUDIO_FRAME_SIZE );

                memset( &pkt, 0, sizeof( pkt ) );

                while( ret >= 0 && !got_audio )
                {
                        // Check if the buffer already contains the samples required
                        if ( audio_used >= *samples && ignore == 0 )
                        {
                                got_audio = 1;
                                break;
                        }

                        // Read a packet
                        ret = av_read_frame( context, &pkt );

                int len = pkt.size;
                uint8_t *ptr = pkt.data;
                        int data_size;

                        // We only deal with video from the selected video_index
                        while ( ptr != NULL && ret >= 0 && pkt.stream_index == index && len > 0 )
                        {
                                // Decode the audio
                                ret = avcodec_decode_audio( codec_context, temp, &data_size, ptr, len );

                                if ( ret < 0 )
                                {
                                        ret = 0;
                                        break;
                                }

                                len -= ret;
                                ptr += ret;

                                if ( data_size > 0 )
                                {
                                        int size_out = audio_resample( resample, &audio_buffer[ audio_used * *channels ], temp, data_size / ( codec_context->channels * sizeof( int16_t ) ) );

                                        audio_used += size_out;

                                        // Handle ignore
                                        while ( ignore && audio_used > *samples )
                                        {
                                                ignore --;
                                                audio_used -= *samples;
                                                memmove( audio_buffer, &audio_buffer[ *samples * *channels ], audio_used * sizeof( int16_t ) );
                                        }
                                }

                                // If we're behind, ignore this packet
                                float current_pts = (float)pkt.pts / 1000000.0;
                                double discrepancy = mlt_properties_get_double( properties, "discrepancy" );
                                if ( current_pts != 0 && real_timecode != 0 )
                                {
                                        if ( discrepancy != 1 )
                                                discrepancy = ( discrepancy + ( real_timecode / current_pts ) ) / 2;
                                        else
                                                discrepancy = real_timecode / current_pts;
                                        if ( discrepancy > 0.9 && discrepancy < 1.1 )
                                                discrepancy = 1.0;
                                        else
                                                discrepancy = floor( discrepancy + 0.5 );

                                        if ( discrepancy == 0 )
                                                discrepancy = 1.0;

                                        mlt_properties_set_double( properties, "discrepancy", discrepancy );
                                }

                                if ( !ignore && discrepancy * current_pts <= ( real_timecode - 0.02 ) )
                                        ignore = 1;
                        }

                        // We're finished with this packet regardless
                        av_free_packet( &pkt );
                }

                *buffer = mlt_pool_alloc( *samples * *channels * sizeof( int16_t ) );
                mlt_properties_set_data( frame_properties, "audio", *buffer, 0, ( mlt_destructor )mlt_pool_release, NULL );

                // Now handle the audio if we have enough
                if ( audio_used >= *samples )
                {
                        memcpy( *buffer, audio_buffer, *samples * *channels * sizeof( int16_t ) );
                        audio_used -= *samples;
                        memmove( audio_buffer, &audio_buffer[ *samples * *channels ], audio_used * *channels * sizeof( int16_t ) );
                }
                else
                {
                        memset( *buffer, 0, *samples * *channels * sizeof( int16_t ) );
                }
                
                // Store the number of audio samples still available
                mlt_properties_set_int( properties, "audio_used", audio_used );

                // Release the temporary audio
                mlt_pool_release( temp );
        }
        else
        {
                // Get silence and don't touch the context
                frame->get_audio = NULL;
                mlt_frame_get_audio( frame, buffer, format, frequency, channels, samples );
        }

        // Regardless of speed, we expect to get the next frame (cos we ain't too bright)
        mlt_properties_set_position( properties, "audio_expected", position + 1 );

        // Unlock the mutex now
        pthread_mutex_unlock( &avformat_mutex );

        return 0;
}

/** Set up audio handling.
*/

static void producer_set_up_audio( mlt_producer this, mlt_frame frame )
{
        // Get the properties
        mlt_properties properties = mlt_producer_properties( this );

        // Fetch the audio_context
        AVFormatContext *context = mlt_properties_get_data( properties, "audio_context", NULL );

        // Get the audio_index
        int index = mlt_properties_get_int( properties, "audio_index" );

        // Lock the mutex now
        pthread_mutex_lock( &avformat_mutex );

        // Deal with audio context
        if ( context != NULL && index != -1 )
        {
                // Get the frame properties
                mlt_properties frame_properties = mlt_frame_properties( frame );

                // Get the audio stream
                AVStream *stream = context->streams[ index ];

                // Get codec context
                AVCodecContext *codec_context = &stream->codec;

                // Get the codec
                AVCodec *codec = mlt_properties_get_data( properties, "audio_codec", NULL );

                // Initialise the codec if necessary
                if ( codec == NULL )
                {
                        // Find the codec
                        codec = avcodec_find_decoder( codec_context->codec_id );

                        // If we don't have a codec and we can't initialise it, we can't do much more...
                        if ( codec != NULL && avcodec_open( codec_context, codec ) >= 0 )
                        {
                                // Now store the codec with its destructor
                                mlt_properties_set_data( properties, "audio_codec", codec_context, 0, producer_codec_close, NULL );

                        }
                        else
                        {
                                // Remember that we can't use this later
                                mlt_properties_set_int( properties, "audio_index", -1 );
                        }
                }

                // No codec, no show...
                if ( codec != NULL )
                {
                        frame->get_audio = producer_get_audio;
                        mlt_properties_set_data( frame_properties, "avformat_producer", this, 0, NULL, NULL );
                }
        }

        // Unlock the mutex now
        pthread_mutex_unlock( &avformat_mutex );
}

/** Our get frame implementation.
*/

static int producer_get_frame( mlt_producer this, mlt_frame_ptr frame, int index )
{
        // Create an empty frame
        *frame = mlt_frame_init( );

        // Update timecode on the frame we're creating
        mlt_frame_set_position( *frame, mlt_producer_position( this ) );

        // Set the position of this producer
        mlt_properties_set_position( mlt_frame_properties( *frame ), "avformat_position", mlt_producer_get_in( this ) + mlt_producer_position( this ) );

        // Set up the video
        producer_set_up_video( this, *frame );

        // Set up the audio
        producer_set_up_audio( this, *frame );

        // Set the aspect_ratio
        mlt_properties_set_double( mlt_frame_properties( *frame ), "aspect_ratio", mlt_properties_get_double( mlt_producer_properties( this ), "aspect_ratio" ) );

        // Calculate the next timecode
        mlt_producer_prepare_next( this );

        return 0;
}