[FFmpeg-user] Quality Reduced when Burning Subtitles

Veronica & Stephen McGuckin VSMcGuckin at outlook.com
Mon Sep 6 15:50:48 EEST 2021

Hello Moritz,

Thank you for your follow up. I have attached a word document which provides the console output. I have also attached a screen shot showing the file data as reported by Mediainfo. It shows the file size as 143 MB and the bit rate as 279 b/s. As you can see from the output I didn't get a syntax error (or at least I think I didn't). By the way how can I tell from the output which CRF actually takes effect?

Once again thanks for any advice you can provide.



-----Original Message-----
From: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> On Behalf Of Moritz Barsnick
Sent: 05 September 2021 15:33
To: FFmpeg user discussions <ffmpeg-user at ffmpeg.org>
Subject: Re: [FFmpeg-user] Quality Reduced when Burning Subtitles
On Sun, Sep 05, 2021 at 13:43:22 +0000, Veronica & Stephen McGuckin wrote:
> ffmpeg -i c:\video\input.mkv -filter_complex "[0:v][0:s]overlay[v]" 
> -c:v libx265 -pix_fmt yuv420p10le -profile:v high  -x265-params 
> "-crf=10 -film -hdr10+=1 -preset slow" -map "[v]" -map 0:a:0 -c:a copy 
> c:\video\output.mkv

Please show us the complete, uncut console output of the command. It would e.g. show which CRF actually takes effect.

I would actually expect an error from this option:
  -x265-params "-crf=10 -film -hdr10+=1 -preset slow"
That's not the correct syntax for x265-params.


    Set x265 options using a list of key=value couples separated by ":". See x265 --help for a list of options.
    For example to specify libx265 encoding options with ‘-x265-params’:
      ffmpeg -i input -c:v libx265 -x265-params crf=26:psy-rd=1 output.mp4

Perhaps you meant to use those "x265-params" as actual ffmpeg options.

> When the conversion is complete the output file is 143 mb with a bit rate of 279 b/s.

I honestly doubt the 279 b/s. That would mean your video is 4299537 seconds long (if you mean 143 MB size - 537442 seconds if you mean 143 Mb). Did you mean 279 kbit/s?

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