Attachment 457 Details for Bug 725 – decode.c ffmpeg/libav audio decode and openal playback native example.

decode.c ffmpeg/libav audio decode and openal playback native example.

decode.c (text/x-csrc), 6.70 KB, created by Xerxes Rånby on 2013-04-24 23:07:36 CEST

(hide)

Description:

Filename:

MIME Type:

Creator: Xerxes Rånby

Created: 2013-04-24 23:07:36 CEST

Size: 6.70 KB

patch

obsolete

>/*
> * ffmpeg/libav audio decode and playback using openal
> *
> *
> * sources of inspiration:
> * http://blinkingblip.wordpress.com/2011/10/08/decoding-and-playing-an-audio-stream-using-libavcodec-libavformat-and-libao/
> * http://git.libav.org/?p=libav.git;a=blob;f=libavcodec/api-example.c;hb=HEAD
> * http://kcat.strangesoft.net/openal-tutorial.html
> *
> * compile:
> * gcc decode.c -lavformat -lopenal
> *
> * Cheers
> * Xerxes RÃ¥nby
> */
>
>#include <stdio.h>
>
>#include <libavcodec/avcodec.h>
>#include <libavformat/avformat.h>
>#include <libavutil/avutil.h>
>
>#include <AL/al.h>
>#include <AL/alc.h>
>
>void die(const char* message)
>{
>    fprintf(stderr, "%s\n", message);
>    exit(1);
>}
>
>int main(int argc, char* argv[])
>{
>    if (argc < 2) {
>        die("Please provide the file path as the first argument");
>    }
>
>    const char* input_filename = argv[1];
>
>    // This call is necessarily done once in your app to initialize
>    // libavformat to register all the muxers, demuxers and protocols.
>    av_register_all();
>
>    // A media container
>    AVFormatContext* container = 0;
>
>    if (avformat_open_input(&container, input_filename, NULL, NULL) < 0) {
>        die("Could not open file");
>    }
>
>    if (av_find_stream_info(container) < 0) {
>        die("Could not find file info");
>    }
>
>    int stream_id = -1;
>
>    // To find the first audio stream. This process may not be necessary
>    // if you can gurarantee that the container contains only the desired
>    // audio stream
>    int i;
>    for (i = 0; i < container->nb_streams; i++) {
>        if (container->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
>            stream_id = i;
>            break;
>        }
>    }
>
>    if (stream_id == -1) {
>        die("Could not find an audio stream");
>    }
>
>    // Find the apropriate codec and open it
>    AVCodecContext* codec_context = container->streams[stream_id]->codec;
>    AVCodec* codec = avcodec_find_decoder(codec_context->codec_id);
>
>    if (!avcodec_open(codec_context, codec) < 0) {
>        die("Could not find open the needed codec");
>    }
>
>    // To initalize openal for playback
>    ALCdevice *dev;
>    ALCcontext *ctx;
>    dev = alcOpenDevice(NULL);
>    if(!dev)
>    {
>        fprintf(stderr, "Oops\n");
>        return 1;
>    }
>    ctx = alcCreateContext(dev, NULL);
>    alcMakeContextCurrent(ctx);
>    if(!ctx)
>    {
>        fprintf(stderr, "Oops2\n");
>        return 1;
>    }
>
>    int initBuffer = 1;
>    int bufferNumber = 0;
>#define NUM_BUFFERS 3
>#define BUFFER_SIZE 4096
>    ALuint source, buffers[NUM_BUFFERS];
>    ALuint frequency = 44100;
>    ALenum format = AL_FORMAT_STEREO16;
>
>    alGenBuffers(NUM_BUFFERS, buffers);
>    alGenSources(1, &source);
>    if(alGetError() != AL_NO_ERROR)
>    {
>        fprintf(stderr, "Error generating :(\n");
>        return 1;
>    }
>
>    // libav
>    AVPacket packet;
>    AVFrame* decodedFrame;
>    decodedFrame=avcodec_alloc_frame();
>    int len;
>
>    while (1) {
>
>        // Read one packet into `packet`
>        if (av_read_frame(container, &packet) < 0) {
>            break;  // End of stream. Done decoding.
>        }
>
>        if(packet.stream_index!=stream_id) {
>			// Skip Video and subtitle packets
>            printf("V");
>            continue;
>        }
>        printf("A");
>        // Decodes audio data from `packet` into the frame
>
>        while( packet.size >0) {
>            int finishedFrame=0;
>            len = avcodec_decode_audio4(codec_context, decodedFrame, &finishedFrame, &packet);
>
>            if(len<0) {
>                printf("error");
>                break;  // Error in decoding
>            }
>
>            if (finishedFrame) {
>			   // Decoded data is now available in
>			   // decodedFrame->data[0]
>			   
>               int data_size = av_samples_get_buffer_size(NULL, codec_context->channels,
>                                                       decodedFrame->nb_samples,
>                                                       codec_context->sample_fmt, 1);
>
>               // OpenAL consumes buffers in the background
>               // we first need to initialize the OpenAL buffers then
>               // start continous playback.
>               if(initBuffer) {
>                   alBufferData(buffers[bufferNumber], format, decodedFrame->data[0], data_size, frequency);
>                   if(alGetError() != AL_NO_ERROR) {
>                       fprintf(stderr, "Error loading :(\n");
>                       return 1;
>                   }
>
>                   if(bufferNumber==2){
>                       // all buffers queued
>                       alSourceQueueBuffers(source, NUM_BUFFERS, buffers);
>                       // start playback
>                       alSourcePlay(source);
>                       if(alGetError() != AL_NO_ERROR) {
>                           fprintf(stderr, "Error starting :(\n");
>                           return 1;
>                       }
>                       initBuffer=0;
>                   }
>
>                   // update buffer number to fill
>                   bufferNumber=(bufferNumber+1)%3;
>               } else {
>				   // OpenAL is playing in the background.
>				   // one new frame with audio data is ready
>				   
>                   // first wait for openal to release one buffer
>                   ALuint buffer;
>                   ALint val;
>                   do {
>                       alGetSourcei(source, AL_BUFFERS_PROCESSED, &val);
>                   } while (val <=0);
>                 
>                   // fill and requeue the empty buffer
>                   alSourceUnqueueBuffers(source, 1, &buffer);
>                   alBufferData(buffer, format, decodedFrame->data[0], data_size, frequency);
>                   alSourceQueueBuffers(source, 1, &buffer);
>                   if(alGetError() != AL_NO_ERROR) {
>                       fprintf(stderr, "Error buffering :(\n");
>                       return 1;
>                   }
>                 
>                   //Restart openal playback if needed
>                   alGetSourcei(source, AL_SOURCE_STATE, &val);
>                   if(val != AL_PLAYING)
>                       alSourcePlay(source);
>                }
>            }
>
>            //There may be more than one frame of audio data
>            //inside the packet.
>            packet.size-=len;
>            packet.data+=len;
>        } // while packet.size > 0
>    } // while more packets exist inside container.
>
>    av_close_input_file(container);
>
>    // Wait for openal to finish playback of any remaining buffers.
>    ALint val;
>    do {
>       alGetSourcei(source, AL_SOURCE_STATE, &val);
>    } while(val == AL_PLAYING);
>
>    // Free OpenAL resources
>    alDeleteSources(1, &source);
>    alDeleteBuffers(NUM_BUFFERS, buffers);
>
>    alcMakeContextCurrent(NULL);
>    alcDestroyContext(ctx);
>    alcCloseDevice(dev);
>
>    fprintf(stdout, "Done playing. Exiting...");
>
>    return 0;
>}

Actions: View

Attachments on bug 725: 457