lavc: set AVCodecContext.codec in avcodec_get_context_defaults3().

This way, if the AVCodecContext is allocated for a specific codec, the
caller doesn't need to store this codec separately and then pass it
again to avcodec_open2().

It also allows to set codec private options using av_opt_set_* before
opening the codec.

1 files changed, 12 insertions, 5 deletions

diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 9cdae22305..fa609534a5 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -630,6 +630,18 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, AVCodec *codec, AVD
     if (avcodec_is_open(avctx))
         return 0;
 
+    if ((!codec && !avctx->codec)) {
+        av_log(avctx, AV_LOG_ERROR, "No codec provided to avcodec_open2().\n");
+        return AVERROR(EINVAL);
+    }
+    if ((codec && avctx->codec && codec != avctx->codec)) {
+        av_log(avctx, AV_LOG_ERROR, "This AVCodecContext was allocated for %s, "
+               "but %s passed to avcodec_open2().\n", avctx->codec->name, codec->name);
+        return AVERROR(EINVAL);
+    }
+    if (!codec)
+        codec = avctx->codec;
+
     if (avctx->extradata_size < 0 || avctx->extradata_size >= FF_MAX_EXTRADATA_SIZE)
         return AVERROR(EINVAL);
 
@@ -649,11 +661,6 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, AVCodec *codec, AVD
         goto end;
     }
 
-    if(avctx->codec || !codec) {
-        ret = AVERROR(EINVAL);
-        goto end;
-    }
-
     avctx->internal = av_mallocz(sizeof(AVCodecInternal));
     if (!avctx->internal) {
         ret = AVERROR(ENOMEM);