PR #24128 opened by ngaullier
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24128
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24128.patch
Use case: interlaced AVC Intra is typically missing the required information
for proper tff detection.
Currently, the decoder defaults to tff, but the parser defaults to progressive.
./ffmpeg -f lavfi -i testsrc=1920x1080 -codec libx264 -pix_fmt yuv422p10le \
-x264-params avcintra-class=100:tff=1 -frames 1 tff.h264
./ffprobe tff.h264 -of flat -show_entries
stream=field_order:frame=interlaced_frame,top_field_first
Before:
frames.frame.0.interlaced_frame=1
frames.frame.0.top_field_first=1
streams.stream.0.field_order="progressive"
After:
frames.frame.0.interlaced_frame=1
frames.frame.0.top_field_first=1
streams.stream.0.field_order="tt"
Issue since field_order setting in 3f1a7ceb2c604deff.
>From 9e94cff9dcd4d5f4abfd483a6d39d263a73007b6 Mon Sep 17 00:00:00 2001
From: Nicolas Gaullier <[email protected]>
Date: Thu, 13 Aug 2026 17:00:42 +0200
Subject: [PATCH] avcodec/h264_parser: align field_order default with the
decoder
Use case: interlaced AVC Intra is typically missing the required information
for proper tff detection.
Currently, the decoder defaults to tff, but the parser defaults to progressive.
./ffmpeg -f lavfi -i testsrc=1920x1080 -codec libx264 -pix_fmt yuv422p10le \
-x264-params avcintra-class=100:tff=1 -frames 1 tff.h264
./ffprobe tff.h264 -of flat -show_entries
stream=field_order:frame=interlaced_frame,top_field_first
Before:
frames.frame.0.interlaced_frame=1
frames.frame.0.top_field_first=1
streams.stream.0.field_order="progressive"
After:
frames.frame.0.interlaced_frame=1
frames.frame.0.top_field_first=1
streams.stream.0.field_order="tt"
Issue since field_order setting in 3f1a7ceb2c604deff.
Signed-off-by: Nicolas Gaullier <[email protected]>
---
libavcodec/h264_parser.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/libavcodec/h264_parser.c b/libavcodec/h264_parser.c
index 9d64fc603f..af43cad609 100644
--- a/libavcodec/h264_parser.c
+++ b/libavcodec/h264_parser.c
@@ -423,6 +423,7 @@ static inline int parse_nal_units(AVCodecParserContext *s,
if (sps->frame_mbs_only_flag) {
p->picture_structure = PICT_FRAME;
+ s->field_order = AV_FIELD_PROGRESSIVE;
} else {
if (get_bits1(&nal.gb)) { // field_pic_flag
p->picture_structure = PICT_TOP_FIELD +
get_bits1(&nal.gb); // bottom_field_flag
@@ -541,8 +542,11 @@ static inline int parse_nal_units(AVCodecParserContext *s,
s->field_order = AV_FIELD_TT;
else if (field_poc[0] > field_poc[1])
s->field_order = AV_FIELD_BB;
- else
- s->field_order = AV_FIELD_PROGRESSIVE;
+ else if (sps->mb_aff) {
+ /* Default to top field first
+ * This is the same as what the decoder does */
+ s->field_order = AV_FIELD_TT;
+ }
}
} else {
if (p->picture_structure == PICT_TOP_FIELD)
--
2.52.0
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