Opened 6 years ago

Closed 6 years ago

Last modified 6 years ago

#2725 closed defect (invalid)

"Static" Video causes buffer underflows

Reported by: jdachik01 Owned by:
Priority: normal Component: undetermined
Version: git-master Keywords:
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no

Description

A video containing static (replicating loss of video signal) causes ffmpeg to throw buffer underflow errors when transcoding to MPEG-2 (1080i).

ffmpeg -i BVV.mpg -s 1920x1080 -top 1 -aspect 16:9 -threads 16 -vcodec mpeg2video -vb 10600k -minrate 10600k -maxrate 10600k -bufsize 4M -r 29.97 -pix_fmt yuv420p -bf 2 -g 15 -y -acodec ac3 -dialnorm -24 -ar 48000 -ab 192k -f mpegts BV_i.mpg

ffmpeg version N-54233-g86190af

Attachments (2)

BVV.mpg (2.3 MB) - added by jdachik01 6 years ago.
Input/source file
BV_i.log (2.9 KB) - added by jdachik01 6 years ago.
Log file showing errors

Change History (6)

Changed 6 years ago by jdachik01

Input/source file

Changed 6 years ago by jdachik01

Log file showing errors

comment:1 Changed 6 years ago by michael

  • Resolution set to invalid
  • Status changed from new to closed

Your bitrate is too low for this video. If you want to encode at this bitrate you can enable trellis and increase lmax but quality will suffer.
Ive improved the printed warning to suggest these

comment:2 Changed 6 years ago by jdachik01

Would you be able to provide the exact syntax that would allow encoding at these low bit rates?

This is constant bit rate encoding, but quality for this video is not crucial.

comment:3 Changed 6 years ago by jdachik01

You can disregard, I was able to find settings that work.

Thank you!

comment:4 Changed 6 years ago by jdachik01

I was able to make usable video with these settings:
-trellis 1
-lmax 420*QP2LAMBDA

Hope this helps anyone affected by this issue. Thank you for pointing out the options I should invoke.

And FYI - even though the -lmax setting seems to be geared toward VBR, these options worked with my CBR output.

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