Hi,
I am using Martin Böhme example from:
http://www.inb.uni-luebeck.de/~boehme/using_libavcodec.html to open the
video file and read it then implement libavcodec codec to get audio stream.
I have several attempts so far but no luck and keeping errors due to my lack
of understand how to process and save audio as wav (using defaults from
libavcodec) from video.
I am using Microsoft Visual studio 2008 and here the coding so far:
#include <libavcodec\avcodec.h>
#include <libavformat\avformat.h>
#define INBUF_SIZE 4096
int main(int argc, char *argv[]) {
FILE *outputFile;
unsigned int i, audioStream;
int frame_size, out_size, enout_size, enoutbuf_size, len;
short *samples;
AVCodecContext *pCodecCtx, *audioEn;
AVCodec *pCodec, *aCodec;
AVFormatContext *pFormatCtx;
CHAR filename[1027];
uint8_t *outbuf, *enoutbuf;
AVPacket packet;
av_register_all();
if(av_open_input_file(&pFormatCtx, filename, NULL, 0, NULL)!=0) return -1;
if(av_find_stream_info(pFormatCtx)<0)return -1;
dump_format(pFormatCtx, 0, filename, false);
//Find audio stream
for(i=0; i < pFormatCtx->nb_streams; i++){
if(pFormatCtx->streams[i]->codec->codec_type==CODEC_TYPE_AUDIO)
{
audioStream=i;
break;
}
}
pCodecCtx=pFormatCtx->streams[audioStream]->codec;
// Find the decoder for the audio stream
pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
if(pCodec==NULL){
fprintf(stderr, "Cannot find decoder");
return -1; // Codec not found
}
if(avcodec_open(pCodecCtx,pCodec)<0) return -1;
outbuf = (uint8_t*)malloc(AVCODEC_MAX_AUDIO_FRAME_SIZE);
aCodec=avcodec_find_encoder(CODEC_ID_PCM_S16LE);
if(pCodec==NULL){
fprintf(stderr, "Cannot find decoder");
return -1; // Codec not found
}
//setting up encoder
audioEn = avcodec_alloc_context();
audioEn->bit_rate = 1411000;
audioEn->sample_rate = 44100;
audioEn->channels = 2;
audioEn->sample_fmt = SAMPLE_FMT_S16;
if(avcodec_open(audioEn,aCodec)<0){
fprintf(stderr, "Could not open encoder codec");
std::cin.get();
}
frame_size = audioEn->frame_size;
samples = (short*)malloc(frame_size * 2 * audioEn->channels);
enoutbuf_size = 10000;
enoutbuf = (uint8_t*)malloc(enoutbuf_size);
outputFile = fopen(".\\temp1.wav", "wb");
if (!outputFile) {
fprintf(stderr, "could not open %s\n", outputFile);
std::cin.get();
exit(1);
}
while(av_read_frame(pFormatCtx, &packet)>=0){
if(packet.stream_index==audioStream){
for(;;){
if (packet.size == 0)
break;
while(packet.size >0){
out_size = AVCODEC_MAX_AUDIO_FRAME_SIZE;
// Decode audio frame
len = avcodec_decode_audio3(pCodecCtx, (short *)outbuf,
&out_size, &packet);
if (len < 0) {
fprintf(stderr, "Error while decoding\n");
exit(1);
}
if (out_size > 0) {
enout_size=avcodec_encode_audio(audioEn, enoutbuf,
enoutbuf_size, samples);
fwrite(enoutbuf, 1, enout_size, outputFile);
}
packet.size -= len;
packet.data += len;
}
}
av_free_packet(&packet);
}
}
fclose(outputFile);
free(outbuf);
// Close the codec
avcodec_close(pCodecCtx);
// Close the video file
av_close_input_file(pFormatCtx);
}
Regards,
Yusuke Kenta
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