avcodec/mediacodecdec: clarify delay_flush specific code

As of 2a0eb8685, ff_mediacodec_dec_is_flushing() only returns
true in delay_flush mode. Make this more obvious by adding
delay_flush to the if statement.

Signed-off-by: Matthieu Bouron <matthieu.bouron@gmail.com>
Signed-off-by: Aman Gupta <aman@tmm1.net>
(cherry picked from commit 6a7a84b2d1)

libavcodec/mediacodecdec.c

@@ -419,27 +419,9 @@ static int mediacodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
     MediaCodecH264DecContext *s = avctx->priv_data;
     int ret;
 
-    /*
-     * MediaCodec.flush() discards both input and output buffers, thus we
-     * need to delay the call to this function until the user has released or
-     * renderered the frames he retains.
-     *
-     * After we have buffered an input packet, check if the codec is in the
-     * flushing state. If it is, we need to call ff_mediacodec_dec_flush.
-     *
-     * ff_mediacodec_dec_flush returns 0 if the flush cannot be performed on
-     * the codec (because the user retains frames). The codec stays in the
-     * flushing state.
-     *
-     * ff_mediacodec_dec_flush returns 1 if the flush can actually be
-     * performed on the codec. The codec leaves the flushing state and can
-     * process again packets.
-     *
-     * ff_mediacodec_dec_flush returns a negative value if an error has
-     * occurred.
-     *
-     */
-    if (ff_mediacodec_dec_is_flushing(avctx, s->ctx)) {
+    /* In delay_flush mode, wait until the user has released or rendered
+       all retained frames. */
+    if (s->delay_flush && ff_mediacodec_dec_is_flushing(avctx, s->ctx)) {
         if (!ff_mediacodec_dec_flush(avctx, s->ctx)) {
             return AVERROR(EAGAIN);
         }

libavcodec/mediacodecdec_common.c

@@ -764,6 +764,18 @@ int ff_mediacodec_dec_receive(AVCodecContext *avctx, MediaCodecDecContext *s,
     return AVERROR(EAGAIN);
 }
 
+/*
+* ff_mediacodec_dec_flush returns 0 if the flush cannot be performed on
+* the codec (because the user retains frames). The codec stays in the
+* flushing state.
+*
+* ff_mediacodec_dec_flush returns 1 if the flush can actually be
+* performed on the codec. The codec leaves the flushing state and can
+* process again packets.
+*
+* ff_mediacodec_dec_flush returns a negative value if an error has
+* occurred.
+*/
 int ff_mediacodec_dec_flush(AVCodecContext *avctx, MediaCodecDecContext *s)
 {
     if (!s->surface || atomic_load(&s->refcount) == 1) {