[FFmpeg-devel] [RFC] LPCM 24 bits support

[Måns Rullgård]

Giuliano Pochini <pochini at shiny.it> writes:

> Hi all.
>
> I have a music DVD with a DVD-V content without video and a stereo
> 96KHz/24 soundtrack. ffmpeg doesn't support it. Below is my first attempt
> to add support for that format. It "almost" works, but I need help.
>
> First, I don't know how to add a new codec properly. I just replaced
> CODEC_ID_PCM_S16BE with CODEC_ID_LPCM_S24 in libavformat/mpeg.c in order to
> make ffmpeg use my code.
>
> The data is shuffled in blocks 12 bytes long. How can I tell the upper
> layers of ffmpeg to not send anything that is not a multiple of 12 bytes ?
>
> The (commented out) debug lines show that the function receives data in
> batches 2004 bytes long. However the last 12 bytes are always 00, 00, 00,
> 00, 00, 00, 00, 00, d2, 01, d1, 01. I guess there is something in the
> container that should be skipped.
>
> ffmpeg does not support 24 bits audio, or am I overlooking something ?
>
> TIA for you help.
>
> diff -dupr ffmpeg__orig/libavcodec/adpcm.c ffmpeg/libavcodec/adpcm.c
> --- ffmpeg__orig/libavcodec/adpcm.c	2008-02-06 12:37:37.000000000 +0000
> +++ ffmpeg/libavcodec/adpcm.c	2008-03-23 22:26:48.000000000 +0000

24-bit DVD audio is not ADPCM, so this code is misplaced.

-- 
M?ns Rullg?rd
mans at mansr.com