avcodec/encode: Set AV_PKT_FLAG_KEY based upon AV_CODEC_PROP_INTRA_ONLY

Currently, the AV_PKT_FLAG_KEY is automatically set for audio encoders;
yet this is wrong, as both MLP and TrueHD have non-keyframes. So set it
based upon AV_CODEC_PROP_INTRA_ONLY (from the corresponding
AVCodecDescriptor) instead. This also sets it for some video codecs,
which is intended.

Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/encode.c

@@ -235,12 +235,9 @@ static int encode_simple_internal(AVCodecContext *avctx, AVPacket *avpkt)
             }
         }
         if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
-            /* NOTE: if we add any audio encoders which output non-keyframe packets,
-             *       this needs to be moved to the encoders, but for now we can do it
-             *       here to simplify things */
-            avpkt->flags |= AV_PKT_FLAG_KEY;
             avpkt->dts = avpkt->pts;
         }
+        avpkt->flags |= avci->intra_only_flag;
     }
 
     if (avci->draining && !got_packet)
@@ -553,6 +550,8 @@ int ff_encode_preinit(AVCodecContext *avctx)
         }
         avctx->sw_pix_fmt = frames_ctx->sw_format;
     }
+    if (avctx->codec_descriptor->props & AV_CODEC_PROP_INTRA_ONLY)
+        avctx->internal->intra_only_flag = AV_PKT_FLAG_KEY;
 
     return 0;
 }

libavcodec/internal.h

@@ -153,6 +153,13 @@ typedef struct AVCodecInternal {
     uint8_t *byte_buffer;
     unsigned int byte_buffer_size;
 
+    /**
+     * This is set to AV_PKT_FLAG_KEY for encoders that encode intra-only
+     * formats (i.e. whose codec descriptor has AV_CODEC_PROP_INTRA_ONLY set).
+     * This is used to set said flag generically for said encoders.
+     */
+    int intra_only_flag;
+
     void *frame_thread_encoder;
 
     EncodeSimpleContext es;