[FFmpeg-devel] [PATCH]Fix AC3-in-avi for the remaining cases

[Justin Ruggles]

On 01/01/2011 03:03 PM, Carl Eugen Hoyos wrote:

> Hi!
> 
> Current svn produces avi files that don't playback on any player when muxing 
> AC3 with 32kHz/320kB, 32kHz/384kB and 44.1kHz/384kB.
> I believe Justin suggested to set blkalign to maximum frame size (first 
> patch).
> An alternative is to just fix the failing cases (second patch).
> 
> Opinions?
> 
> Please comment, Carl Eugen
> 
> 

> Index: libavformat/riff.c
> ===================================================================
> --- libavformat/riff.c	(revision 26183)
> +++ libavformat/riff.c	(working copy)
> @@ -370,12 +370,10 @@
>          av_log(enc, AV_LOG_WARNING, "requested bits_per_coded_sample (%d) and actually stored (%d) differ\n", enc->bits_per_coded_sample, bps);
>      }
>  
> -    if (enc->codec_id == CODEC_ID_MP2 || enc->codec_id == CODEC_ID_MP3 || enc->codec_id == CODEC_ID_AC3) {
> +    if (enc->codec_id == CODEC_ID_MP2 || enc->codec_id == CODEC_ID_MP3) {
>          blkalign = enc->frame_size; //this is wrong, but it seems many demuxers do not work if this is set correctly
>          //blkalign = 144 * enc->bit_rate/enc->sample_rate;
> -        //For high bitrate AC-3, set blkalign to maximum bytes per frame value
> -        //to allow playback on WMP and MPlayer
> -        if (enc->bit_rate > 384000)
> +    } else if (enc->codec_id == CODEC_ID_AC3) {
>              blkalign = 3840;
>      } else if (enc->codec_id == CODEC_ID_ADPCM_G726) { //
>          blkalign = 1;


I like this version better.

Regarding the other patch, if it would be better for some reason to use
a more accurate value for AC-3 we could do:

switch (enc->sample_rate) {
     8000: blkalign =  960;
    11025: blkalign =  697;
    12000: blkalign =  640;
    16000: blkalign = 1920;
    22050: blkalign = 1394;
    24000: blkalign = 1280;
    32000: blkalign = 3840;
    44100: blkalign = 2788;
    48000: blkalign = 2560;
}

-Justin