avcodec: add AV_CODEC_FLAG_DROPCHANGED to flags

Discard decoded frames which differ from first decoded frame in stream.

1 files changed, 46 insertions, 1 deletions

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index a32ff2f..6c31166 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -740,7 +740,7 @@ static int apply_cropping(AVCodecContext *avctx, AVFrame *frame)
 int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
 {
     AVCodecInternal *avci = avctx->internal;
-    int ret;
+    int ret, changed;
 
     av_frame_unref(frame);
 
@@ -765,6 +765,51 @@ int attribute_align_arg avcodec_receive_frame(AVCodecContext *avctx, AVFrame *fr
 
     avctx->frame_number++;
 
+    if (avctx->flags & AV_CODEC_FLAG_DROPCHANGED) {
+
+        if (avctx->frame_number == 1) {
+            avci->initial_format = frame->format;
+            switch(avctx->codec_type) {
+            case AVMEDIA_TYPE_VIDEO:
+                avci->initial_width  = frame->width;
+                avci->initial_height = frame->height;
+                break;
+            case AVMEDIA_TYPE_AUDIO:
+                avci->initial_sample_rate = frame->sample_rate ? frame->sample_rate :
+                                                                 avctx->sample_rate;
+                avci->initial_channels       = frame->channels;
+                avci->initial_channel_layout = frame->channel_layout;
+                break;
+            }
+        }
+
+        if (avctx->frame_number > 1) {
+            changed = avci->initial_format != frame->format;
+
+           switch(avctx->codec_type) {
+            case AVMEDIA_TYPE_VIDEO:
+                changed |= avci->initial_width  != frame->width ||
+                           avci->initial_height != frame->height;
+                break;
+            case AVMEDIA_TYPE_AUDIO:
+                changed |= avci->initial_sample_rate    != frame->sample_rate ||
+                           avci->initial_sample_rate    != avctx->sample_rate ||
+                           avci->initial_channels       != frame->channels ||
+                           avci->initial_channel_layout != frame->channel_layout;
+                break;
+            }
+
+            if (changed) {
+                avci->changed_frames_dropped++;
+                av_log(avctx, AV_LOG_INFO, "dropped changed frame #%d pts %"PRId64
+                                            " drop count: %d \n",
+                                            avctx->frame_number, frame->pts,
+                                            avci->changed_frames_dropped);
+                av_frame_unref(frame);
+                return AVERROR_INPUT_CHANGED;
+            }
+        }
+    }
     return 0;
 }