optimise dissolve case

[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.

        NOTE: We need to have a valid [PAL or NTSC] frame rate before we can determine the 
        number of frames in the file. However, this is at odds with the way things work - the 
        constructor needs to provide in/out points before the user of the producer is able
        to specify properties :-/. However, the PAL/NTSC distinction applies to all producers
        and while we currently accept whatever the producer provides, this will not work in
        the more general case. Plans are afoot... and this one will work without modification
        (in theory anyway ;-)).
*/

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 );
//      fprintf( stderr, "AVFORMAT: open %d %s\n", error, file );
        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 = 0;

        // 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 );
                void *frame_release = NULL;
                void *buffer_release = NULL;
                size += *width * 2;
                uint8_t *buf = mlt_pool_allocate( size, &buffer_release );
                output = mlt_pool_allocate( sizeof( AVPicture ), &frame_release );
                memset( output, 0, sizeof( AVPicture ) );
                avpicture_fill( output, buf, PIX_FMT_YUV422, *width, *height );
                mlt_properties_set_data( properties, "video_output_frame_release", frame_release, 0, ( mlt_destructor )mlt_pool_release, NULL );
                mlt_properties_set_data( properties, "video_output_buffer_release", buffer_release, 0, ( mlt_destructor )mlt_pool_release, NULL );
                mlt_properties_set_data( properties, "video_output_frame", output, 0, NULL, NULL );
                mlt_properties_set_data( properties, "video_output_buffer", buf, 0, NULL, 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", 0 );
                        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
                void *release = NULL;
                *buffer = mlt_pool_allocate( size, &release );
                memcpy( *buffer, image, size );

                // Set this on the frame properties
                mlt_properties_set_data( frame_properties, "image_release", release, 0, ( mlt_destructor )mlt_pool_release, NULL );
                mlt_properties_set_data( frame_properties, "image", *buffer, size, NULL, 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 )
                        {
                                current_time = ( double )pkt.pts / 1000000.0;

                                // Decode the image
                                // Wouldn't it be great if I could use this...
                                //if ( (float)pkt.pts / 1000000.0 >= real_timecode )
                                ret = avcodec_decode_video( codec_context, &frame, &got_picture, pkt.data, pkt.size );

                                if ( got_picture )
                                {
                                        // Handle ignore
                                        if ( current_time < real_timecode )
                                        {
                                                ignore = 0;
                                                got_picture = 0;
                                        }
                                        else if ( current_time >= real_timecode )
                                        {
                                                ignore = 0;
                                        }
                                        else if ( got_picture && 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;
                        void *release = NULL;
                        uint8_t *image = mlt_properties_get_data( properties, "current_image", &size );

                        if ( image == NULL || size != *width * *height * 2 )
                        {
                                void *current_image_release = NULL;
                                size = *width * ( *height + 1 ) * 2;
                                image = mlt_pool_allocate( size, &current_image_release );
                                mlt_properties_set_data( properties, "current_image_release", current_image_release, 0, ( mlt_destructor )mlt_pool_release, NULL );
                                mlt_properties_set_data( properties, "current_image", image, size, NULL, NULL );
                        }

                        *buffer = mlt_pool_allocate( size, &release );
                        img_convert( output, PIX_FMT_YUV422, (AVPicture *)&frame, codec_context->pix_fmt, *width, *height );
                        memcpy( image, output->data[ 0 ], size );
                        memcpy( *buffer, output->data[ 0 ], size );
                        mlt_properties_set_data( frame_properties, "image_release", release, 0, ( mlt_destructor )mlt_pool_release, NULL );
                        mlt_properties_set_data( frame_properties, "image", *buffer, size, NULL, 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;

                        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\n", 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 );

                                // Set to the real timecode
                                av_seek_frame( context, -1, 0 );
                        }
                        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 )
        {
                // Audio buffer release pointer
                void *buffer_release = NULL;

                // Allocate the audio buffer
                audio_buffer = mlt_pool_allocate( AVCODEC_MAX_AUDIO_FRAME_SIZE * sizeof( int16_t ), &buffer_release );

                // And store it on properties for reuse
                mlt_properties_set_data( properties, "audio_buffer_release", buffer_release, 0, ( mlt_destructor )mlt_pool_release, NULL );
                mlt_properties_set_data( properties, "audio_buffer", audio_buffer, 0, NULL, 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;
                void *temp_release = NULL;
                int16_t *temp = mlt_pool_allocate( sizeof( int16_t ) * AVCODEC_MAX_AUDIO_FRAME_SIZE, &temp_release );

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

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

                // Now handle the audio if we have enough
                if ( audio_used >= *samples )
                {
                        void *buffer_release = NULL;
                        *buffer = mlt_pool_allocate( *samples * *channels * sizeof( int16_t ), &buffer_release );
                        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 ) );
                        mlt_properties_set_data( frame_properties, "audio_release", buffer_release, 0, ( mlt_destructor )mlt_pool_release, NULL );
                        mlt_properties_set_data( frame_properties, "audio", *buffer, 0, NULL, NULL );
                }
                else
                {
                        frame->get_audio = NULL;
                        mlt_frame_get_audio( frame, buffer, format, frequency, channels, samples );
                        audio_used = 0;
                }
                
                // 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_release );
        }
        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;
}