avcodec: add AVCodecContext.sw_pix_fmt

This carries the pixel format that would be used if it were not for
hardware acceleration. This is equal to AVCodecContext.pix_fmt if
hardware acceleration is not in use.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:     2014-08-09
 
 API changes, most recent first:
 
+201x-xx-xx - xxxxxxx - lavc 56.8.0 - avcodec.h
+  Add AVCodecContext.sw_pix_fmt.
+
 2014-11-xx - xxxxxxx - lavf 56.06.3 - avformat.h
   Add AVFormatContext.avoid_negative_ts.
 

libavcodec/avcodec.h

@@ -2800,6 +2800,13 @@ typedef struct AVCodecContext {
      * - encoding: unused
      */
     AVRational framerate;
+
+    /**
+     * Nominal unaccelerated pixel format, see AV_PIX_FMT_xxx.
+     * - encoding: unused.
+     * - decoding: Set by libavcodec before calling get_format()
+     */
+    enum AVPixelFormat sw_pix_fmt;
 } AVCodecContext;
 
 /**

libavcodec/utils.c

@@ -665,10 +665,13 @@ int ff_get_buffer(AVCodecContext *avctx, AVFrame *frame, int flags)
     if (ret < 0)
         return ret;
 
-    if (hwaccel && hwaccel->alloc_frame) {
+    if (hwaccel) {
+        if (hwaccel->alloc_frame) {
             ret = hwaccel->alloc_frame(avctx, frame);
             goto end;
         }
+    } else
+        avctx->sw_pix_fmt = avctx->pix_fmt;
 
 #if FF_API_GET_BUFFER
 FF_DISABLE_DEPRECATION_WARNINGS
@@ -933,6 +936,10 @@ int ff_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt)
     while (fmt[n] != AV_PIX_FMT_NONE)
         ++n;
 
+    av_assert0(n >= 1);
+    avctx->sw_pix_fmt = fmt[n - 1];
+    av_assert2(!is_hwaccel_pix_fmt(avctx->sw_pix_fmt));
+
     choices = av_malloc_array(n + 1, sizeof(*choices));
     if (!choices)
         return AV_PIX_FMT_NONE;

libavcodec/version.h

@@ -29,7 +29,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVCODEC_VERSION_MAJOR 56
-#define LIBAVCODEC_VERSION_MINOR  7
+#define LIBAVCODEC_VERSION_MINOR  8
 #define LIBAVCODEC_VERSION_MICRO  0
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \