[FFmpeg-user] Quality Reduced when Burning Subtitles

[Paul B Mahol]

On Sun, Sep 5, 2021 at 3:43 PM Veronica & Stephen McGuckin <
VSMcGuckin at outlook.com> wrote:

> Hello,
>
> I am trying to overlay pgs subtitles onto a 4K video. I have extracted 10
> minute to make sure I have the correct ffmpeg coding. The input file is 5.6
> gigabytes with a bit rate of 78.6 Mb/s. I am using the following ffmpeg
> commands.
>
> 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
>
>
Make sure that overlay filter uses 10bit format by setting appropriate
filter option if main format is also 10bit.


> When the conversion is complete the output file is 143 mb with a bit rate
> of 279 b/s. I am surprised the output file is so small. I would have
> expected it to be also around 5 Gb. I am concerned that I will have lost
> some of the quality. Have I somehow got the wrong parameters?
>
> Any help will be appreciated.
>
> Stephen McGuckin
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