[Ffmpeg-devel] [PATCH] DTS multichannel

[Kostya]

On Wed, Apr 25, 2007 at 04:25:18PM -0400, Justin Ruggles wrote:
> Hi,
> 
> Here is a patch to add multichannel support to the native DTS decoder.
> It also utilizes the downmixing coeffients, which is not done currently.
>  The default coefficients are based on the comments at the bottom of
> dtsdata.h.
> 
> downmix 5.1 to stereo:
> ffmpeg -f dts -i stream.dts -acodec pcm_s16le -ac 2 stream-stereo.wav
> 
> copy 5.1 direct to wav:
> ffmpeg -f dts -i stream.dts -acodec pcm_s16le -ac 6 stream-5p1.wav
> 
> Note that channel reordering is not done yet, so the multichannel output
> would be in MPEG-2/4 channel order (C,L,R,LS,RS,LFE).
> 
> -Justin

Looks ok except minor nitpick: 

> @@ -1140,10 +1156,24 @@
>      }
>      //set AVCodec values with parsed data
>      avctx->sample_rate = s->sample_rate;
> -    avctx->channels = 2; //FIXME
> +
> +    channels = s->prim_channels + !!s->lfe;
> +    if(avctx->channels == 0) {
> +        avctx->channels = channels;
> +    } else if(channels < avctx->channels) {
> +        av_log(avctx, AV_LOG_ERROR, "DTS source channels are less than specified: output to %d channels.\n", channels);
> +        avctx->channels = channels;

This should be IMHO av_log(avctx, AV_LOG_DEBUG, "Downmixing to %d channels\n", channels)
or dropped at all

> +    }
> +    if(avctx->channels == 2) {
> +        s->output = DCA_STEREO;
> +    } else if(avctx->channels != channels) {
> +        av_log(avctx, AV_LOG_ERROR, "Cannot downmix DTS to %d channels.\n", avctx->channels);
> +        return -1;
> +    }
> +

And feel free to work on multichannel code in DCA decoder.