[Libav-user] G.711 audio in mkv container

[Alex Grosu]

Ok, I figured it out. The frame_size should not have been set to 2560, 
but instead let it in the initial state (0). After that, the frames are 
coming with 1280 as frame_size

So anyway, for anyone who want to put G7111 audio codec in a mkv 
container (Windows), here is the header:

c->codec_id = CODEC_ID_PCM_ALAW;
c->codec_type = CODEC_TYPE_AUDIO;

c->sample_fmt = SAMPLE_FMT_S16;

c->flags = CODEC_FLAG_GLOBAL_HEADER;

c->bit_rate = 64000;
c->sample_rate = 8000;
c->channels = 1;
c->channel_layout = 1;
waveFormatEX = malloc(sizeof(WAVEFORMATEXTENSIBLE) + 
FF_INPUT_BUFFER_PADDING_SIZE);
waveFormatEX->Format.wFormatTag = WAVE_FORMAT_EXTENSIBLE;
waveFormatEX->Format.nChannels = 1;
waveFormatEX->Format.nSamplesPerSec = 8000;
waveFormatEX->Format.wBitsPerSample = 16;
waveFormatEX->Format.nBlockAlign = 2;
waveFormatEX->Format.nAvgBytesPerSec = 16000;
waveFormatEX->Format.cbSize = sizeof(WAVEFORMATEXTENSIBLE);
waveFormatEX->Samples.wSamplesPerBlock = 0;
waveFormatEX->dwChannelMask = KSAUDIO_SPEAKER_MONO;
waveFormatEX->SubFormat = KSDATAFORMAT_SUBTYPE_ALAW;
c->extradata = (uint8_t*)waveFormatEX;
c->extradata_size = waveFormatEX->Format.cbSize;


This is working for me


On 9/23/2016 2:19 PM, Alex Grosu wrote:
>
> Arghh, I forgot to add in my previous mail these settings :
>
> c->sample_fmt = SAMPLE_FMT_S16;
>
> c->flags = CODEC_FLAG_GLOBAL_HEADER;
>
>
> On 9/23/2016 2:16 PM, Alex Grosu wrote:
>>
>> One correction,
>>
>> c->frame_size = 2560 (not 2650, typo)
>>
>> Sorry for this
>>
>>
>>
>> On 9/23/2016 2:13 PM, Alex Grosu wrote:
>>> Dear all
>>>
>>> I am having some issues in creating a G711 audio mkv container with 
>>> libavcodec on windows.
>>> I set the codec context (header) like this:
>>> c->codec_id = CODEC_ID_PCM_ALAW;
>>> c->codec_type = CODEC_TYPE_AUDIO;
>>> c->bit_rate = 64000;
>>> c->sample_rate = 8000;
>>> c->channels = 1;
>>> c->frame_size = 2650;
>>> c->channel_layout = 1;
>>> waveFormatEX = malloc(sizeof(WAVEFORMATEXTENSIBLE) + 
>>> FF_INPUT_BUFFER_PADDING_SIZE);
>>> waveFormatEX->Format.wFormatTag = WAVE_FORMAT_EXTENSIBLE;
>>> waveFormatEX->Format.nChannels = 1;
>>> waveFormatEX->Format.nSamplesPerSec = 8000;
>>> waveFormatEX->Format.wBitsPerSample = 16;
>>> waveFormatEX->Format.nBlockAlign = 2;
>>> waveFormatEX->Format.nAvgBytesPerSec = 16000;
>>> waveFormatEX->Format.cbSize = sizeof(WAVEFORMATEXTENSIBLE);
>>> waveFormatEX->Samples.wSamplesPerBlock = 0;
>>> waveFormatEX->dwChannelMask = KSAUDIO_SPEAKER_MONO;
>>> waveFormatEX->SubFormat = KSDATAFORMAT_SUBTYPE_ALAW;
>>> c->extradata = (uint8_t*)waveFormatEX;
>>> c->extradata_size = waveFormatEX->Format.cbSize;
>>>
>>> The mkv container is created, ffplay can play it without problems:
>>>
>>> This is the what ffplay outputs when playing the file:
>>>
>>> Input #0, matroska,webm, from 'c:\Users\alex\Bus 
>>> standard-37-Enregistreur Xebra3
>>> --2016-09-15(0h 1m 0s)\Cam 1 Flux audio.mkv':
>>>   Metadata:
>>>     encoder         : Lavf52.78.1
>>>   Duration: 00:01:52.00, start: 0.000000, bitrate: 34 kb/s
>>>     Stream #0:0: Audio: pcm_alaw ([6][0][0][0] / 0x0006), 8000 Hz, 1 
>>> channels, s
>>> 16, 64 kb/s (default)
>>>     Stream #0:1(fra): Subtitle: subrip (default)
>>>    8.94 M-A: -0.000 fd=   0 aq=  421KB vq=    0KB sq=    0B f=0/0
>>>
>>> The sound can be heard witthout problems. The file should have ~ 1 
>>> minute, but ffplay say the duration is 1:52
>>>
>>> The vlc player instead has issues in playing the file. The sound is 
>>> heard but with "gaps", something related to pts?
>>> This is the info from vlc about the file:
>>> Type: Audio
>>> Codec: PCM ALAW(alaw)
>>> Channels: Mono
>>> Sample rate: 8000 Hz
>>> Bits per sample: 16
>>> And here are some warnings while playing the file:
>>> corewarning: playback way too early (-170000): playing silence
>>>
>>> coredebug: inserting 1360 zeroes
>>>
>>> corewarning: playback way too early (-150000): playing silence
>>>
>>> coredebug: inserting 1200 zeroes
>>>
>>> corewarning: playback way too early (-170000): playing silence
>>>
>>> coredebug: inserting 1360 zeroes
>>>
>>> corewarning: playback way too early (-150000): playing silence
>>>
>>>
>>>
>>> Can somebody please guide how to properly set G.711 
>>> (CODEC_ID_PCM_ALAW) in libavcodec?
>>> Thank you a lot for reading this long post
>>>
>>>
>>> _______________________________________________
>>> Libav-user mailing list
>>> Libav-user at ffmpeg.org
>>> http://ffmpeg.org/mailman/listinfo/libav-user
>>
>>
>>
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