lavc: Add a flag in AVPacket to discard packet after decoding. Discard frames after decoding based on the flag.

Signed-off-by: Sasi Inguva <isasi@google.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/avcodec.h

@@ -1621,6 +1621,12 @@ typedef struct AVPacket {
 } AVPacket;
 #define AV_PKT_FLAG_KEY     0x0001 ///< The packet contains a keyframe
 #define AV_PKT_FLAG_CORRUPT 0x0002 ///< The packet content is corrupted
+/**
+ * Flag is used to discard packets which are required to maintain valid
+ * decoder state but are not required for output and should be dropped
+ * after decoding.
+ **/
+#define AV_PKT_FLAG_DISCARD   0x0004
 
 enum AVSideDataParamChangeFlags {
     AV_SIDE_DATA_PARAM_CHANGE_CHANNEL_COUNT  = 0x0001,

libavcodec/utils.c

@@ -784,6 +784,12 @@ int ff_init_buffer_info(AVCodecContext *avctx, AVFrame *frame)
             }
         }
         add_metadata_from_side_data(pkt, frame);
+
+        if (pkt->flags & AV_PKT_FLAG_DISCARD) {
+            frame->flags |= AV_FRAME_FLAG_DISCARD;
+        } else {
+            frame->flags = (frame->flags & ~AV_FRAME_FLAG_DISCARD);
+        }
     } else {
         frame->pkt_pts = AV_NOPTS_VALUE;
         av_frame_set_pkt_pos     (frame, -1);
@@ -2247,7 +2253,9 @@ fail:
             if(ret == tmp.size)
                 ret = avpkt->size;
         }
-
+        if (picture->flags & AV_FRAME_FLAG_DISCARD) {
+            *got_picture_ptr = 0;
+        }
         if (*got_picture_ptr) {
             if (!avctx->refcounted_frames) {
                 int err = unrefcount_frame(avci, picture);
@@ -2343,6 +2351,11 @@ int attribute_align_arg avcodec_decode_audio4(AVCodecContext *avctx,
                 frame->sample_rate = avctx->sample_rate;
         }
 
+
+        if (frame->flags & AV_FRAME_FLAG_DISCARD) {
+            *got_frame_ptr = 0;
+        }
+
         side= av_packet_get_side_data(avctx->internal->pkt, AV_PKT_DATA_SKIP_SAMPLES, &side_size);
         if(side && side_size>=10) {
             avctx->internal->skip_samples = AV_RL32(side);