avcodec/mediacodec: return error when buffer is released a second time

If the caller does any further processing (e.g. with AImageReader), it's very important
to know if he can expect the frame to actually arrive at the surface or not.
This provides a clearly detectable error in case the buffer was released multiple times
*or* the codec was flushed in the meantime.

libavcodec/mediacodec.c

@@ -96,6 +96,8 @@ int av_mediacodec_release_buffer(AVMediaCodecBuffer *buffer, int render)
                "Releasing output buffer %zd (%p) ts=%"PRId64" with render=%d [%d pending]\n",
                buffer->index, buffer, buffer->pts, render, atomic_load(&ctx->hw_buffer_count));
         return ff_AMediaCodec_releaseOutputBuffer(ctx->codec, buffer->index, render);
+    } else if (render) {
+        return AVERROR(ENOENT);
     }
 
     return 0;
@@ -114,7 +116,7 @@ int av_mediacodec_render_buffer_at_time(AVMediaCodecBuffer *buffer, int64_t time
         return ff_AMediaCodec_releaseOutputBufferAtTime(ctx->codec, buffer->index, time);
     }
 
-    return 0;
+    return AVERROR(ENOENT);
 }
 
 #else

libavcodec/mediacodec.h

@@ -81,7 +81,9 @@ typedef struct MediaCodecBuffer AVMediaCodecBuffer;
  * @param buffer the buffer to render
  * @param render 1 to release and render the buffer to the surface or 0 to
  * discard the buffer
- * @return 0 on success, < 0 otherwise
+ * @return 0 on success, < 0 otherwise.
+ * AVERROR(ENOENT) is returned when trying to render a buffer that has already
+ * been released.
  */
 int av_mediacodec_release_buffer(AVMediaCodecBuffer *buffer, int render);
 
@@ -95,6 +97,8 @@ int av_mediacodec_release_buffer(AVMediaCodecBuffer *buffer, int render);
  * @param buffer the buffer to render
  * @param time timestamp in nanoseconds of when to render the buffer
  * @return 0 on success, < 0 otherwise
+ * AVERROR(ENOENT) is returned when trying to render a buffer that has already
+ * been released.
  *
  * [0]: https://developer.android.com/reference/android/media/MediaCodec#releaseOutputBuffer(int,%20long)
  */

libavcodec/version.h

@@ -30,7 +30,7 @@
 #include "version_major.h"
 
 #define LIBAVCODEC_VERSION_MINOR  11
-#define LIBAVCODEC_VERSION_MICRO 100
+#define LIBAVCODEC_VERSION_MICRO 101
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \