[FFmpeg-devel] ffmpeg g723

Zalewa PL zalewapl at gmail.com
Sun Mar 11 00:28:39 CET 2012

Hah! Bluecherry. I was suspecting that you are using their product. Thankfully I have some experience with this card and I can assure that it is possible to get the audio from this card using the 'decode-g72x' tool. Now that you have given us the ffmpeg command line that you use to create the video stream, here's what you have to do. Bash commands incoming:

# Creates a named pipe
mkfifo /tmp/audio_raw_stream

# Extract audio data from the ALSA device. Decode it from g723 to PCM.
# NOTE: Make sure this runs in background. You can't close this
# pipeline or the streaming from ffmpeg will stop.
arecord -Dplughw:1,0,1 -traw | decode-g72x -l -3>  /tmp/audio_raw_stream

# ffmpeg now reads from the named pipe instead of the ALSA device
# and decodes audio properly.
ffmpeg -f s16le -acodec pcm_s16le -ac 1 -ar 8000 -i /tmp/audio_raw_stream -f v4l2 -i
/dev/video1 -r 29.97 -b:v 800 -qmax 51 -async 1 -ar 11025 -ac 1 -ab 24k
-acodec libmp3lame -vcodec libx264 -f flv rtmp://localhost/live/livestream

Trust me: unless I made a mistake in the parameters, this will work. I've been there. I've done that.

Robert Watson wrote:

> The card is manufactured by BlueCherry and has v4l2&  alsa opensource
> drivers.  This is what they said:
> Since Alsa currently doesn't have a format for G.723, the driver shows it
> as unsigned 8-bit PCM audio.  We have sent a patch that was included in
> alsa-kernel (hopefully getting synced to mainline soon). But this only
> defines the correct format, it doesn't change the way you handle it at all.
>   You must convert G.723-24 (3-bit samples at 8khz) yourself.
> And, thanks for your help :)
> Robert
> On Sat, Mar 10, 2012 at 2:32 PM, Benjamin Larsson<benjamin at southpole.se>wrote:
>> On 03/09/2012 10:24 PM, Robert Watson wrote:
>>> I was wondering if you could help with using ffmpeg to process the audio
>>> input from a capture card.  The card has v4l2 and alsa drivers. The card
>>> outputs G.723-24 (3-bit samples at 8khz).  Was the g723 code you wrote
>>> committed into the ffmpeg core?  What command line should I use to capture
>>> the audio from the card?
>>> Thanks, Robert
>> G.723 and G.723.1 is not the same. So it wont work. And probably the card
>> doesn't output G723. Elaborate in detail and we might be able to help.
>> MvH
>> Benjamin Larsson
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