lavc: add avcodec_is_open().

It allows to check whether an AVCodecContext is open in a documented
way. Right now the undocumented way this check is done in lavf/lavc is
by checking whether AVCodecContext.codec is NULL. However it's desirable
to be able to set AVCodecContext.codec before avcodec_open2().

5 files changed, 20 insertions, 4 deletions

diff --git a/doc/APIchanges b/doc/APIchanges
index 7545fa51dc..87de464ebb 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -13,6 +13,9 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
+2012-01-31 - xxxxxxx - lavc 54.01.0
+  Add avcodec_is_open() function.
+
 2012-01-30 - xxxxxxx - lavu 51.22.0 - intfloat.h
   Add a new installed header libavutil/intfloat.h with int/float punning
   functions.
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index a6bb6863f2..284c7f8cb8 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -4183,4 +4183,10 @@ enum AVMediaType avcodec_get_type(enum CodecID codec_id);
  */
 const AVClass *avcodec_get_class(void);
 
+/**
+ * @return a positive value if s is open (i.e. avcodec_open2() was called on it
+ * with no corresponding avcodec_close()), 0 otherwise.
+ */
+int avcodec_is_open(AVCodecContext *s);
+
 #endif /* AVCODEC_AVCODEC_H */
diff --git a/libavcodec/options.c b/libavcodec/options.c
index c416b4aa4f..52fc66400a 100644
--- a/libavcodec/options.c
+++ b/libavcodec/options.c
@@ -485,7 +485,7 @@ AVCodecContext *avcodec_alloc_context3(AVCodec *codec){
 
 int avcodec_copy_context(AVCodecContext *dest, const AVCodecContext *src)
 {
-    if (dest->codec) { // check that the dest context is uninitialized
+    if (avcodec_is_open(dest)) { // check that the dest context is uninitialized
         av_log(dest, AV_LOG_ERROR,
                "Tried to copy AVCodecContext %p into already-initialized %p\n",
                src, dest);
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 34a4122d5d..3ee6b09f74 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -627,6 +627,9 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, AVCodec *codec, AVD
     int ret = 0;
     AVDictionary *tmp = NULL;
 
+    if (avcodec_is_open(avctx))
+        return 0;
+
     if (avctx->extradata_size < 0 || avctx->extradata_size >= FF_MAX_EXTRADATA_SIZE)
         return AVERROR(EINVAL);
 
@@ -1803,3 +1806,8 @@ enum AVMediaType avcodec_get_type(enum CodecID codec_id)
 
     return AVMEDIA_TYPE_UNKNOWN;
 }
+
+int avcodec_is_open(AVCodecContext *s)
+{
+    return !!s->internal;
+}
diff --git a/libavformat/utils.c b/libavformat/utils.c
index 9c59947fb7..1b2239a068 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2006,7 +2006,7 @@ static int try_decode_frame(AVStream *st, AVPacket *avpkt, AVDictionary **option
     AVFrame picture;
     AVPacket pkt = *avpkt;
 
-    if(!st->codec->codec){
+    if (!avcodec_is_open(st->codec)) {
         AVDictionary *thread_opt = NULL;
 
         codec = avcodec_find_decoder(st->codec->codec_id);
@@ -2354,8 +2354,7 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
     // close codecs which were opened in try_decode_frame()
     for(i=0;i<ic->nb_streams;i++) {
         st = ic->streams[i];
-        if(st->codec->codec)
-            avcodec_close(st->codec);
+        avcodec_close(st->codec);
     }
     for(i=0;i<ic->nb_streams;i++) {
         st = ic->streams[i];