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().

(cherry picked from commit af08d9aeea)

Conflicts:

	doc/APIchanges

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:   2011-04-18
 
 API changes, most recent first:
 
+2012-02-17 - xxxxxxx - lavc 53.35.0
+  Add avcodec_is_open() function.
+
 2012-01-15 - lavc 53.34.0
   New audio encoding API:
   b2c75b6 Add CODEC_CAP_VARIABLE_FRAME_SIZE capability for use by audio

libavcodec/avcodec.h

@@ -4737,4 +4737,10 @@ 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 */

libavcodec/options.c

@@ -634,7 +634,7 @@ AVCodecContext *avcodec_alloc_context(void){
 
 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);

libavcodec/utils.c

@@ -637,6 +637,9 @@ 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);
 
@@ -1836,3 +1839,8 @@ enum AVMediaType avcodec_get_type(enum CodecID codec_id)
 
     return AVMEDIA_TYPE_UNKNOWN;
 }
+
+int avcodec_is_open(AVCodecContext *s)
+{
+    return !!s->internal;
+}

libavcodec/version.h

@@ -21,7 +21,7 @@
 #define AVCODEC_VERSION_H
 
 #define LIBAVCODEC_VERSION_MAJOR 53
-#define LIBAVCODEC_VERSION_MINOR 34
+#define LIBAVCODEC_VERSION_MINOR 35
 #define LIBAVCODEC_VERSION_MICRO  0
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \

libavformat/utils.c

@@ -2137,7 +2137,7 @@ 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);
@@ -2487,8 +2487,7 @@ 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];