#11231: alphamerge complex filter delays video several seconds
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Reporter: degradox | Type: defect
Status: new | Priority: normal
Component: | Version:
undetermined | unspecified
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Summary of the bug: using complex filter with alphamerge caused audio-
video desync.
How to reproduce:
When converting normally, the output has audio and video synced, like the
input:
{{{
% ffmpeg -y -i input_good.mp4 -map 0:v -map 0:a -c:v libx264 -profile:v
high -level:v 4.2 -pix_fmt yuv420p \
-r 60 -b:v 600k -preset fast -c:a aac -b:a 80k -ar 48000 -ac 2 -fps_mode
cfr -nostdin output_good.mp4
}}}
Using filter advances somehow the video. The first minutes it's about 7
seconds. At the end the video ends about 13 seconds earlier than audio, so
there's the last frame stuck for that time:
{{{
% ffmpeg -y \
-i input_good.mp4 \
-filter_complex "\
[0:v]scale=1920:1080:force_original_aspect_ratio=decrease,setpts=PTS-
STARTPTS [scaled_main]; \
color=c=black@0:s=1280x720:d=10000 [blank_overlay]; \
[blank_overlay]format=gray [mask_trim]; \
[blank_overlay][mask_trim]alphamerge [overlay_stream]; \
[scaled_main][overlay_stream]overlay=x=main_w-overlay_w-0:y=main_h-
overlay_h-0:eof_action=pass:shortest=0 [outv]" \
-map "[outv]" -map 0:a -c:v libx264 -profile:v high -level:v 4.2
-pix_fmt yuv420p -r 60 -b:v 600k -preset fast \
-c:a aac -b:a 80k -ar 48000 -ac 2 -fps_mode cfr -nostdin
output_desynced.mp4
}}}
Both outputs have the same duration as the input, 51 minutes 54 seconds.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11231>
FFmpeg <https://ffmpeg.org>
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