lavc: allow using AVCodecContext.hw_frames_ctx for decoding

For now it will only be used by the default get_buffer2 callback for
allocating hw frames.

1 files changed, 17 insertions, 7 deletions

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index c4bf708e3b..ace761dd56 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -3078,15 +3078,25 @@ typedef struct AVCodecContext {
     int            nb_coded_side_data;
 
     /**
-     * Encoding only.
+     * A reference to the AVHWFramesContext describing the input (for encoding)
+     * or output (decoding) frames. The reference is set by the caller and
+     * afterwards owned (and freed) by libavcodec.
      *
-     * For hardware encoders configured to use a hwaccel pixel format, this
-     * field should be set by the caller to a reference to the AVHWFramesContext
-     * describing input frames. AVHWFramesContext.format must be equal to
-     * AVCodecContext.pix_fmt.
+     * - decoding: This field should be set by the caller from the get_format()
+     *             callback. The previous reference (if any) will always be
+     *             unreffed by libavcodec before the get_format() call.
      *
-     * This field should be set before avcodec_open2() is called and is
-     * afterwards owned and managed by libavcodec.
+     *             If the default get_buffer2() is used with a hwaccel pixel
+     *             format, then this AVHWFramesContext will be used for
+     *             allocating the frame buffers.
+     *
+     * - encoding: For hardware encoders configured to use a hwaccel pixel
+     *             format, this field should be set by the caller to a reference
+     *             to the AVHWFramesContext describing input frames.
+     *             AVHWFramesContext.format must be equal to
+     *             AVCodecContext.pix_fmt.
+     *
+     *             This field should be set before avcodec_open2() is called.
      */
     AVBufferRef *hw_frames_ctx;
 } AVCodecContext;