avcodec/decode: add a flags parameter to ff_reget_buffer()

Some decoders may not need a writable buffer in some specific cases, but only
a reference to the existing buffer with updated frame properties instead, for
the purpose of returning duplicate frames. For this, the
FF_REGET_BUFFER_FLAG_READONLY flag is added, which will prevent potential
allocations and buffer copies when they are not needed.

Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/libavcodec/internal.h b/libavcodec/internal.h
index 5f96414..9db3d36 100644
--- a/libavcodec/internal.h
+++ b/libavcodec/internal.h
@@ -320,11 +320,12 @@ static av_always_inline float ff_exp2fi(int x) {
  */
 int ff_get_buffer(AVCodecContext *avctx, AVFrame *frame, int flags);
 
+#define FF_REGET_BUFFER_FLAG_READONLY 1 ///< the returned buffer does not need to be writable
 /**
- * Identical in function to av_frame_make_writable(), except it uses
- * ff_get_buffer() to allocate the buffer when needed.
+ * Identical in function to ff_get_buffer(), except it reuses the existing buffer
+ * if available.
  */
-int ff_reget_buffer(AVCodecContext *avctx, AVFrame *frame);
+int ff_reget_buffer(AVCodecContext *avctx, AVFrame *frame, int flags);
 
 int ff_thread_can_start_frame(AVCodecContext *avctx);