lavc: add ff_alloc_packet2().

This contains a AVCodecContext thus allowing us to prevent the
error message duplication
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/internal.h

@@ -127,6 +127,7 @@ int avpriv_unlock_avformat(void);
  * ensure the output packet data is large enough, whether provided by the user
  * or allocated in this function.
  *
+ * @param avctx   the AVCodecContext of the encoder
  * @param avpkt   the AVPacket
  *                If avpkt->data is already set, avpkt->size is checked
  *                to ensure it is large enough.
@@ -136,6 +137,8 @@ int avpriv_unlock_avformat(void);
  * @param size    the minimum required packet size
  * @return        0 on success, negative error code on failure
  */
+int ff_alloc_packet2(AVCodecContext *avctx, AVPacket *avpkt, int size);
+
 int ff_alloc_packet(AVPacket *avpkt, int size);
 
 /**

libavcodec/utils.c

@@ -939,26 +939,38 @@ free_and_end:
     goto end;
 }
 
-int ff_alloc_packet(AVPacket *avpkt, int size)
+int ff_alloc_packet2(AVCodecContext *avctx, AVPacket *avpkt, int size)
 {
-    if (size > INT_MAX - FF_INPUT_BUFFER_PADDING_SIZE)
+    if (size < 0 || avpkt->size < 0 || size > INT_MAX - FF_INPUT_BUFFER_PADDING_SIZE) {
+        av_log(avctx, AV_LOG_ERROR, "Size %d invalid\n", size);
         return AVERROR(EINVAL);
+    }
 
     if (avpkt->data) {
         void *destruct = avpkt->destruct;
 
-        if (avpkt->size < size)
+        if (avpkt->size < size) {
+            av_log(avctx, AV_LOG_ERROR, "User packet is too small (%d < %d)\n", avpkt->size, size);
             return AVERROR(EINVAL);
+        }
 
         av_init_packet(avpkt);
         avpkt->destruct = destruct;
         avpkt->size = size;
         return 0;
     } else {
-        return av_new_packet(avpkt, size);
+        int ret = av_new_packet(avpkt, size);
+        if (ret < 0)
+            av_log(avctx, AV_LOG_ERROR, "Failed to allocate packet of size %d\n", size);
+        return ret;
     }
 }
 
+int ff_alloc_packet(AVPacket *avpkt, int size)
+{
+    return ff_alloc_packet2(NULL, avpkt, size);
+}
+
 int attribute_align_arg avcodec_encode_audio2(AVCodecContext *avctx,
                                               AVPacket *avpkt,
                                               const AVFrame *frame,