[FFmpeg-devel] [PATCH 7/7] avcodec: add AV_CODEC_FLAG_CLEAR

[Marton Balint <cus@passwd.hu>]

Signed-off-by: Marton Balint <cus@passwd.hu>
---
 doc/APIchanges             |  3 +++
 doc/codecs.texi            | 14 ++++++++++++++
 libavcodec/avcodec.h       |  4 ++++
 libavcodec/decode.c        |  6 ++++++
 libavcodec/options_table.h |  1 +
 libavcodec/version.h       |  2 +-
 6 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index b6ac8e08e2..e411aa0d91 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,9 @@ The last version increases of all libraries were on 2023-02-09
 
 API changes, most recent first:
 
+2023-12-xx - xxxxxxxxxxx - lavc 60.36.100 - avcodec.h
+  Add AV_CODEC_FLAG_CLEAR.
+
 2023-12-xx - xxxxxxxxxxx - lavu 58.33.100 - imguils.h
   Add av_image_fill_color()
 
diff --git a/doc/codecs.texi b/doc/codecs.texi
index 5b950b4560..0504a535f2 100644
--- a/doc/codecs.texi
+++ b/doc/codecs.texi
@@ -76,6 +76,20 @@ Apply interlaced motion estimation.
 Use closed gop.
 @item output_corrupt
 Output even potentially corrupted frames.
+@item clear
+Clear the contents of the video buffer before decoding the next picture to it.
+
+Usually if only a part of a picture is affected by a decode error then the
+decoder (if it implements error concealment) tries to hide it by interpolating
+pixels from neighbouring areas or in some cases from the previous frame. Even
+without error concealment it is quite likely that the affected area will
+contain pixels from an earlier frame, due to frame pooling.
+
+For quality checking this might not be desirable, because it makes the errors
+less noticable. By using this flag, and combining it with disabled error
+concealment (@code{-ec 0}) it is possible to ensure that no leftover data from
+an earlier frame is presented in areas affected by decode errors.
+
 @end table
 
 @item time_base @var{rational number}
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 7fb44e28f4..97848e942f 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -312,6 +312,10 @@ typedef struct RcOverride{
  * loop filter.
  */
 #define AV_CODEC_FLAG_LOOP_FILTER     (1 << 11)
+/**
+ * Clear frame buffer contents before decoding.
+ */
+#define AV_CODEC_FLAG_CLEAR           (1 << 12)
 /**
  * Only decode/encode grayscale.
  */
diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 2cfb3fcf97..f9b18a2c35 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -1675,6 +1675,12 @@ FF_ENABLE_DEPRECATION_WARNINGS
 
     validate_avframe_allocation(avctx, frame);
 
+    if (avctx->flags & AV_CODEC_FLAG_CLEAR && avctx->codec_type == AVMEDIA_TYPE_VIDEO) {
+        uint32_t color[4] = {0};
+        ptrdiff_t linesize[4] = {frame->linesize[0], frame->linesize[1], frame->linesize[2], frame->linesize[3]};
+        av_image_fill_color(frame->data, linesize, frame->format, color, frame->width, frame->height);
+    }
+
     ret = ff_attach_decode_data(frame);
     if (ret < 0)
         goto fail;
diff --git a/libavcodec/options_table.h b/libavcodec/options_table.h
index ee243d9894..46a7d41c18 100644
--- a/libavcodec/options_table.h
+++ b/libavcodec/options_table.h
@@ -62,6 +62,7 @@ static const AVOption avcodec_options[] = {
 {"frame_duration", "use frame durations", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_FRAME_DURATION}, .unit = "flags"},
 {"pass1", "use internal 2-pass ratecontrol in first  pass mode", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_PASS1 }, INT_MIN, INT_MAX, 0, "flags"},
 {"pass2", "use internal 2-pass ratecontrol in second pass mode", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_PASS2 }, INT_MIN, INT_MAX, 0, "flags"},
+{"clear", "clear frames before decoding", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_CLEAR }, INT_MIN, INT_MAX, V|E|D, "flags"},
 {"gray", "only decode/encode grayscale", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_GRAY }, INT_MIN, INT_MAX, V|E|D, "flags"},
 {"psnr", "error[?] variables will be set during encoding", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_PSNR }, INT_MIN, INT_MAX, V|E, "flags"},
 {"ildct", "use interlaced DCT", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_INTERLACED_DCT }, INT_MIN, INT_MAX, V|E, "flags"},
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 1008fead27..34b059a8a9 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -29,7 +29,7 @@
 
 #include "version_major.h"
 
-#define LIBAVCODEC_VERSION_MINOR  35
+#define LIBAVCODEC_VERSION_MINOR  36
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
-- 
2.35.3

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