lavu/frame: improve AVFrame.opaque[_ref] documentation

Make them match each other, mention interaction with
AV_CODEC_FLAG_COPY_OPAQUE.
This commit is contained in:
Anton Khirnov 2021-01-26 16:59:16 +01:00
parent 81bc7bc52e
commit d732db3a38

View File

@ -470,7 +470,18 @@ typedef struct AVFrame {
int quality;
/**
* for some private data of the user
* Frame owner's private data.
*
* This field may be set by the code that allocates/owns the frame data.
* It is then not touched by any library functions, except:
* - it is copied to other references by av_frame_copy_props() (and hence by
* av_frame_ref());
* - it is set to NULL when the frame is cleared by av_frame_unref()
* - on the caller's explicit request. E.g. libavcodec encoders/decoders
* will copy this field to/from @ref AVPacket "AVPackets" if the caller sets
* @ref AV_CODEC_FLAG_COPY_OPAQUE.
*
* @see opaque_ref the reference-counted analogue
*/
void *opaque;
@ -678,13 +689,18 @@ typedef struct AVFrame {
AVBufferRef *hw_frames_ctx;
/**
* AVBufferRef for free use by the API user. FFmpeg will never check the
* contents of the buffer ref. FFmpeg calls av_buffer_unref() on it when
* the frame is unreferenced. av_frame_copy_props() calls create a new
* reference with av_buffer_ref() for the target frame's opaque_ref field.
* Frame owner's private data.
*
* This is unrelated to the opaque field, although it serves a similar
* purpose.
* This field may be set by the code that allocates/owns the frame data.
* It is then not touched by any library functions, except:
* - a new reference to the underlying buffer is propagated by
* av_frame_copy_props() (and hence by av_frame_ref());
* - it is unreferenced in av_frame_unref();
* - on the caller's explicit request. E.g. libavcodec encoders/decoders
* will propagate a new reference to/from @ref AVPacket "AVPackets" if the
* caller sets @ref AV_CODEC_FLAG_COPY_OPAQUE.
*
* @see opaque the plain pointer analogue
*/
AVBufferRef *opaque_ref;