int perms, int w, int h);
AVFilterBufferRef *ff_null_get_video_buffer(AVFilterLink *link, int perms, int w, int h);
-void ff_null_start_frame(AVFilterLink *link, AVFilterBufferRef *picref);
-void ff_null_draw_slice(AVFilterLink *link, int y, int h, int slice_dir);
-void ff_null_end_frame(AVFilterLink *link);
+/**
+ * Request a picture buffer with a specific set of permissions.
+ *
+ * @param link the output link to the filter from which the buffer will
+ * be requested
+ * @param perms the required access permissions
+ * @param w the minimum width of the buffer to allocate
+ * @param h the minimum height of the buffer to allocate
+ * @return A reference to the buffer. This must be unreferenced with
+ * avfilter_unref_buffer when you are finished with it.
+ */
+AVFilterBufferRef *ff_get_video_buffer(AVFilterLink *link, int perms,
+ int w, int h);
+
+int ff_inplace_start_frame(AVFilterLink *link, AVFilterBufferRef *picref);
+int ff_null_start_frame(AVFilterLink *link, AVFilterBufferRef *picref);
+int ff_null_draw_slice(AVFilterLink *link, int y, int h, int slice_dir);
+int ff_null_end_frame(AVFilterLink *link);
/**
* Notify the next filter of the start of a frame.
* frame need only be valid once draw_slice() is called for that
* portion. The receiving filter will free this reference when
* it no longer needs it.
+ *
+ * @return >= 0 on success, a negative AVERROR on error. This function will
+ * unreference picref in case of error.
*/
-void ff_start_frame(AVFilterLink *link, AVFilterBufferRef *picref);
+int ff_start_frame(AVFilterLink *link, AVFilterBufferRef *picref);
/**
* Notify the next filter that the current frame has finished.
*
* @param link the output link the frame was sent over
+ *
+ * @return >= 0 on success, a negative AVERROR on error
*/
-void ff_end_frame(AVFilterLink *link);
+int ff_end_frame(AVFilterLink *link);
/**
* Send a slice to the next filter.
* from the top slice to the bottom slice if the value is 1,
* from the bottom slice to the top slice if the value is -1,
* for other values the behavior of the function is undefined.
+ *
+ * @return >= 0 on success, a negative AVERROR on error.
*/
-void ff_draw_slice(AVFilterLink *link, int y, int h, int slice_dir);
+int ff_draw_slice(AVFilterLink *link, int y, int h, int slice_dir);
#endif /* AVFILTER_VIDEO_H */