[FFmpeg-devel] [PATCH] libavformat/asfdec_f: add asf video average framerate support

[FFmpeg-devel] [PATCH] libavformat/asfdec_f: add asf video average framerate support

[ZhangXu via ffmpeg-devel]

From: zhangxu <zhangxu@sobey.com>

Refer to Advanced Systems Format (ASF) Specification

Parse AverageTimePerFrame from ExtendedStreamPropertiesObject

Signed-off-by: ZhangXu <zhangxu@sobey.com>
---
 libavformat/asfdec_f.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/libavformat/asfdec_f.c b/libavformat/asfdec_f.c
index 3b46fe01f6..aaff5278d9 100644
--- a/libavformat/asfdec_f.c
+++ b/libavformat/asfdec_f.c
@@ -63,6 +63,8 @@ typedef struct ASFStream {
 
     int64_t packet_pos;
 
+    int64_t avg_time_dur;                ///< the average time duration
+
     uint16_t stream_language_index;
 
     int      palette_changed;
@@ -481,6 +483,7 @@ static int asf_read_ext_stream_properties(AVFormatContext *s)
     int ext_len, payload_ext_ct, stream_ct, i;
     uint32_t leak_rate, stream_num;
     unsigned int stream_languageid_index;
+    uint64_t stream_avg_time_dur;
 
     avio_rl64(pb); // starttime
     avio_rl64(pb); // endtime
@@ -498,7 +501,10 @@ static int asf_read_ext_stream_properties(AVFormatContext *s)
     if (stream_num < 128)
         asf->streams[stream_num].stream_language_index = stream_languageid_index;
 
-    avio_rl64(pb); // avg frametime in 100ns units
+    stream_avg_time_dur = avio_rl64(pb); // avg frametime in 100ns units
+    if (stream_num < 128)
+        asf->streams[stream_num].avg_time_dur = stream_avg_time_dur;
+
     stream_ct      = avio_rl16(pb); // stream-name-count
     payload_ext_ct = avio_rl16(pb); // payload-extension-system-count
 
@@ -838,6 +844,10 @@ static int asf_read_header(AVFormatContext *s)
                     i, st->codecpar->codec_type, asf->dar[i].num, asf->dar[i].den,
                     st->sample_aspect_ratio.num, st->sample_aspect_ratio.den);
 
+            //this field set for video
+            if (asf->streams[i].avg_time_dur && st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
+                av_reduce(&st->avg_frame_rate.num, &st->avg_frame_rate.den, 10000000, asf->streams[i].avg_time_dur, INT_MAX);
+            
             // copy and convert language codes to the frontend
             if (asf->streams[i].stream_language_index < 128) {
                 const char *rfc1766 = asf->stream_languages[asf->streams[i].stream_language_index];
-- 
2.25.1
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[FFmpeg-devel] Re: [PATCH] libavformat/asfdec_f: add asf video average framerate support

[Michael Niedermayer via ffmpeg-devel]

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Hi

On Thu, Oct 09, 2025 at 07:21:09PM +0800, ZhangXu via ffmpeg-devel wrote:
> From: zhangxu <zhangxu@sobey.com>
> 
> Refer to Advanced Systems Format (ASF) Specification
> 
> Parse AverageTimePerFrame from ExtendedStreamPropertiesObject
> 
> Signed-off-by: ZhangXu <zhangxu@sobey.com>
> ---
>  libavformat/asfdec_f.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)

This breaks fate

--- ./tests/ref/fate/wmv3-drm-nodec	2025-09-24 19:09:24.202291445 +0200
+++ tests/data/fate/wmv3-drm-nodec	2025-10-14 01:10:51.797737754 +0200
@@ -10,55 +10,55 @@
 #codec_id 1: wmavoice
 #sample_rate 1: 22050
 #channel_layout_name 1: mono
-0,          0,          0,        0,      282, 0x000d949a
+0,          0,          0,       33,      282, 0x000d949a
 1,          0,          0,        0,     1088, 0x5cd379bb
 1,        435,        435,        0,     1088, 0x8dfa1368
 1,        740,        740,        0,     1088, 0xc0d211be
 1,       1023,       1023,        0,     1088, 0x8238113a
-0,       1208,       1208,        0,      137, 0x903c415e, F=0x0
-0,       1250,       1250,        0,      942, 0xd5b7d2aa, F=0x0
-0,       1291,       1291,        0,      841, 0xaffd8ce6, F=0x0
+0,       1208,       1208,       33,      137, 0x903c415e, F=0x0
+0,       1250,       1250,       33,      942, 0xd5b7d2aa, F=0x0
+0,       1291,       1291,       33,      841, 0xaffd8ce6, F=0x0
 1,       1306,       1306,        0,     1088, 0x9f8924b7


 Also the duration values seem not correct at all

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates

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[FFmpeg-devel] Re: [PATCH] libavformat/asfdec_f: add asf video average framerate support

[via ffmpeg-devel]

Thanks for your reply, I will continue to work on some details
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[FFmpeg-devel] Re: [PATCH] libavformat/asfdec_f: add asf video average framerate support

[via ffmpeg-devel]

Hi， Michael Niedermayer

My modification is to make ASF Demux give a reference frame rate information from the file information.

However, I debugged the fate process and found that if I added the avg_frame_rate information in the stream, the guess_pkt_duration function() in mux.c with the framecrc muxer process would automatically generate the duration based on the avg_frame_rate, which would cause fate's CRC to report an error. So this modification will definitely lead to inconsistent results in fate. 

Do you have any good suggestions for solving this problem?
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