Thanks Luca for your answer.
I have made some progress. I can now encode the audio to PCM_16LE codec. I can
hear the audio but their is a big noise on the audio.
Here below the code to encode audio file to PCM codec:
- (void) extractAudioFromVideoFile:(NSString *)filenameString toFile:(NSString
*)outfilenameString
{
NSLog(@"extractAudioFromVideoFile\n");
const char *inFileName = [filenameString UTF8String];
const char *outFileName = [outfilenameString UTF8String];
av_register_all();
AVFormatContext* inContainer = NULL;
if(avformat_open_input(&inContainer, inFileName, NULL, NULL) < 0)
exit(1);
if(avformat_find_stream_info(inContainer, NULL) < 0)
exit(1);
int videoStreamIndex = -1;
for (unsigned int i = 0; i < inContainer->nb_streams; ++i)
{
if (inContainer->streams[i] && inContainer->streams[i]->codec &&
inContainer->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO)
{
videoStreamIndex = i;
break;
}
}
if (videoStreamIndex == -1)
exit(1);
AVFormatContext* outContainer = NULL;
if(avformat_alloc_output_context2(&outContainer, NULL, NULL, outFileName) <
0)
exit(1);
AVStream *const inStream = inContainer->streams[videoStreamIndex];
AVCodec *const decoder = avcodec_find_decoder(inStream->codec->codec_id);
inStream->codec->sample_fmt = AV_SAMPLE_FMT_S16;
if(!decoder)
exit(1);
if(avcodec_open2(inStream->codec, decoder, NULL) < 0)
exit(1);
AVCodec *encoder = avcodec_find_encoder(AV_CODEC_ID_PCM_S16LE);
AVStream *outStream = avformat_new_stream(outContainer, encoder);
if(!outStream)
exit(1);
outStream->codec->coder_type = AVMEDIA_TYPE_AUDIO;
outStream->codec->sample_fmt = AV_SAMPLE_FMT_S16;
outStream->codec->sample_rate = inStream->codec->sample_rate ;
outStream->codec->channels = inStream->codec->channels ;
if(avcodec_open2(outStream->codec, encoder, NULL) < 0)
exit(1);
FILE *outfile;
if(avio_open(&outContainer->pb, outFileName, AVIO_FLAG_WRITE) < 0)
exit(1);
AVFrame *decodedFrame = avcodec_alloc_frame();
avformat_write_header(outContainer, NULL);
AVPacket decodePacket, copyPacket;
av_init_packet(&decodePacket);
decodePacket.data = NULL;
decodePacket.size = 0;
int got_frame, len;
while(av_read_frame(inContainer, &decodePacket)>=0)
{
if (decodePacket.stream_index == videoStreamIndex)
{
decodedFrame = avcodec_alloc_frame();
len = avcodec_decode_audio4(inStream->codec, decodedFrame,
&got_frame, &decodePacket);
if(got_frame)
{
av_init_packet(©Packet);
avcodec_encode_audio2(outStream->codec,
©Packet,decodedFrame, &got_frame);
copyPacket.pts = decodePacket.pts;
copyPacket.dts = decodePacket.dts;
copyPacket.duration = decodePacket.duration;
NSLog(@"Duration : %i ,PTS : %lld ,DTS :
%lld",copyPacket.duration ,copyPacket.pts, copyPacket.dts);
av_interleaved_write_frame(outContainer, ©Packet);
av_free_packet(©Packet);
}
}
}
av_free_packet(&decodePacket);
av_write_trailer(outContainer);
avio_close(outContainer->pb);
avcodec_free_frame(&decodedFrame);
avformat_free_context(outContainer);
avformat_close_input(&inContainer);
}
Thanks for your support,
Francois
Le 31 août 2013 à 10:29, Luca Barbato <[email protected]> a écrit :
> On 31/08/13 09:44, Francois PEDEBOSCQ Yahoo wrote:
>> Dear All,
>>
>> I am trying to extract the audio track of a video file and to save it
>> into a file. The audio codec of the video I am testing is AC3 but my
>> code should work with any audio codec. WIth the code below, I get an
>> audio file but it's unreadable.
>
> Libav9 uses planar audio as intermediate format, you should either
> "encode" to the right codec or set the right planar audio codec_id in
> the container format.
>
> lu
> _______________________________________________
> libav-api mailing list
> [email protected]
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