[FFmpeg-devel] [PATCH] add AVCodecContext field to specify desired number of channels

[Reimar Döffinger]

Hello,
On Mon, Aug 20, 2007 at 01:57:57PM +0200, Michael Niedermayer wrote:
> On Sun, Aug 19, 2007 at 10:08:13PM +0200, Michael Niedermayer wrote:
> > On Sun, Aug 19, 2007 at 04:56:44PM +0200, Reimar D?ffinger wrote:
> > > Hello,
> > > since the current way of setting ->channels no matter how it is done
> > > will break some codecs I suggest adding a new field.
> > > Also has the advantage that it will be easier to allow handling the
> > > cases where either the number of desired channels changes or the number
> > > of channels in the file changes.
> > > I also think that the current behaviour of dca is not good: if it can't
> > > deliver the requested number of channels it should just use either
> > > something close or the native number instead of failing.
> > > Is it right to add this at the end of the context or should it be near
> > > "channels"?
> > 
> > looks ok though maybe you should wait a day or two before applying it
> > maybe someone, justin, kostya? have some comments
> 
> also dont forget to update the AVOption array un libavcodec/utils.c

Like this?

Greetings,
Reimar D?ffinger
-------------- next part --------------
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 1719b02..0fdc65f 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -33,8 +33,8 @@
 #define AV_STRINGIFY(s)         AV_TOSTRING(s)
 #define AV_TOSTRING(s) #s
 
-#define LIBAVCODEC_VERSION_INT  ((51<<16)+(41<<8)+0)
-#define LIBAVCODEC_VERSION      51.41.0
+#define LIBAVCODEC_VERSION_INT  ((51<<16)+(42<<8)+0)
+#define LIBAVCODEC_VERSION      51.42.0
 #define LIBAVCODEC_BUILD        LIBAVCODEC_VERSION_INT
 
 #define LIBAVCODEC_IDENT        "Lavc" AV_STRINGIFY(LIBAVCODEC_VERSION)
@@ -2123,6 +2123,13 @@ typedef struct AVCodecContext {
      * - decoding: unused
      */
     int64_t timecode_frame_start;
+
+    /**
+     * Decoder should decode to this many channels if it can (0 for default)
+     * - encoding: unused
+     * - decoding: Set by user.
+     */
+    int request_channels;
 } AVCodecContext;
 
 /**
diff --git a/libavcodec/dca.c b/libavcodec/dca.c
index d9bf03a..0426693 100644
--- a/libavcodec/dca.c
+++ b/libavcodec/dca.c
@@ -1158,6 +1158,7 @@ static int dca_decode_frame(AVCodecContext * avctx,
     avctx->bit_rate = s->bit_rate;
 
     channels = s->prim_channels + !!s->lfe;
+    avctx->channels = avctx->request_channels;
     if(avctx->channels == 0) {
         avctx->channels = channels;
     } else if(channels < avctx->channels) {
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 3b19489..609a175 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -753,6 +753,7 @@ static const AVOption options[]={
 {"timecode_frame_start", "GOP timecode frame start number, in non drop frame format", OFFSET(timecode_frame_start), FF_OPT_TYPE_INT, 0, 0, INT_MAX, V|E},
 {"drop_frame_timecode", NULL, 0, FF_OPT_TYPE_CONST, CODEC_FLAG2_DROP_FRAME_TIMECODE, INT_MIN, INT_MAX, V|E, "flags2"},
 {"non_linear_q", "use non linear quantizer", 0, FF_OPT_TYPE_CONST, CODEC_FLAG2_NON_LINEAR_QUANT, INT_MIN, INT_MAX, V|E, "flags2"},
+{"request_channels", "set desired number of audio channels", OFFSET(request_channels), FF_OPT_TYPE_INT, DEFAULT, INT_MIN, INT_MAX, A|D},
 {NULL},
 };