lavc: introduce avcodec_open2() as a replacement for avcodec_open().

Adds support for decoder-private options and makes setting other options
simpler.

libavcodec/avcodec.h

@@ -30,6 +30,7 @@
 #include "libavutil/samplefmt.h"
 #include "libavutil/avutil.h"
 #include "libavutil/cpu.h"
+#include "libavutil/dict.h"
 #include "libavutil/log.h"
 #include "libavutil/pixfmt.h"
 #include "libavutil/rational.h"
@@ -3619,6 +3620,7 @@ int avcodec_default_execute(AVCodecContext *c, int (*func)(AVCodecContext *c2, v
 int avcodec_default_execute2(AVCodecContext *c, int (*func)(AVCodecContext *c2, void *arg2, int, int),void *arg, int *ret, int count);
 //FIXME func typedef
 
+#if FF_API_AVCODEC_OPEN
 /**
  * Initialize the AVCodecContext to use the given AVCodec. Prior to using this
  * function the context has to be allocated.
@@ -3645,8 +3647,45 @@ int avcodec_default_execute2(AVCodecContext *c, int (*func)(AVCodecContext *c2,
  * @param codec The codec to use within the context.
  * @return zero on success, a negative value on error
  * @see avcodec_alloc_context, avcodec_find_decoder, avcodec_find_encoder, avcodec_close
+ *
+ * @deprecated use avcodec_open2
  */
+attribute_deprecated
 int avcodec_open(AVCodecContext *avctx, AVCodec *codec);
+#endif
+
+/**
+ * Initialize the AVCodecContext to use the given AVCodec. Prior to using this
+ * function the context has to be allocated with avcodec_alloc_context().
+ *
+ * The functions avcodec_find_decoder_by_name(), avcodec_find_encoder_by_name(),
+ * avcodec_find_decoder() and avcodec_find_encoder() provide an easy way for
+ * retrieving a codec.
+ *
+ * @warning This function is not thread safe!
+ *
+ * @code
+ * avcodec_register_all();
+ * av_dict_set(&opts, "b", "2.5M", 0);
+ * codec = avcodec_find_decoder(CODEC_ID_H264);
+ * if (!codec)
+ *     exit(1);
+ *
+ * context = avcodec_alloc_context();
+ *
+ * if (avcodec_open(context, codec, opts) < 0)
+ *     exit(1);
+ * @endcode
+ *
+ * @param avctx The context to initialize.
+ * @param options A dictionary filled with AVCodecContext and codec-private options.
+ *                On return this object will be filled with options that were not found.
+ *
+ * @return zero on success, a negative value on error
+ * @see avcodec_alloc_context3(), avcodec_find_decoder(), avcodec_find_encoder(),
+ *      av_dict_set(), av_opt_find().
+ */
+int avcodec_open2(AVCodecContext *avctx, AVCodec *codec, AVDictionary **options);
 
 /**
  * Decode the audio frame of size avpkt->size from avpkt->data into samples.