From 9af7e8045e3e63ab39adedae9a7c11b1c410af26 Mon Sep 17 00:00:00 2001
From: Luca Barbato <lu_zero@gentoo.org>
Date: Sun, 14 Jun 2015 11:45:54 +0200
Subject: [PATCH] lavc: Clarify the behaviour of dimension and format context
fields
The AVCodecContext width, height, coded_width, coded_height and format
are used mainly as decoding hints and they get internally overwritten
during the data parsing stage.
Do not assume they match the last AVFrame provided by
avcodec_decode_video2 and assimilated functions since multi-threading
and other frame reordering might make those values to refer to frames
that will be outputted in the future.
CC: libav-stable@libav.org
---
libavcodec/avcodec.h | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 3440126662b..7edea2c5bce 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -1217,21 +1217,31 @@ typedef struct AVCodecContext {
/* video only */
/**
* picture width / height.
+ *
+ * @note Those fields may not match the values of the last
+ * AVFrame outputted by avcodec_decode_video2 due frame
+ * reordering.
+ *
* - encoding: MUST be set by user.
* - decoding: May be set by the user before opening the decoder if known e.g.
* from the container. Some decoders will require the dimensions
* to be set by the caller. During decoding, the decoder may
- * overwrite those values as required.
+ * overwrite those values as required while parsing the data.
*/
int width, height;
/**
* Bitstream width / height, may be different from width/height e.g. when
* the decoded frame is cropped before being output.
+ *
+ * @note Those field may not match the value of the last
+ * AVFrame outputted by avcodec_decode_video2 due frame
+ * reordering.
+ *
* - encoding: unused
* - decoding: May be set by the user before opening the decoder if known
* e.g. from the container. During decoding, the decoder may
- * overwrite those values as required.
+ * overwrite those values as required while parsing the data.
*/
int coded_width, coded_height;
@@ -1250,8 +1260,14 @@ typedef struct AVCodecContext {
* Pixel format, see AV_PIX_FMT_xxx.
* May be set by the demuxer if known from headers.
* May be overriden by the decoder if it knows better.
+ *
+ * @note This field may not match the value of the last
+ * AVFrame outputted by avcodec_decode_video2 due frame
+ * reordering.
+ *
* - encoding: Set by user.
- * - decoding: Set by user if known, overridden by libavcodec if known
+ * - decoding: Set by user if known, overridden by libavcodec while
+ * parsing the data.
*/
enum AVPixelFormat pix_fmt;
--
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