[FFmpeg-user] Convert flv to mp4. Bad video quality

Flavio Sartoretto flavio.sartoretto1956 at gmail.com
Fri May 28 19:04:28 EEST 2021

Thank you Carl for your clarification.
I obtain good results using -q:v 4
Prof. Flavio Sartoretto
gia' Docente di Calcolo Scientifico
Universita' Ca' Foscari Venezia

On Fri, May 28, 2021 at 5:24 PM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> > Am 28.05.2021 um 11:44 schrieb Michael Koch <astroelectronic at t-online.de>:
> >
> > Am 28.05.2021 um 11:25 schrieb Flavio Sartoretto:
> >> I use ffmpeg in order to convert fname.flv video to mp4:
> >> ffmpeg -i fname.flv -c:v mpeg4 -copyts -loglevel verbose fname.mp4
> >>
> >> The video quality of my output is bad. How can I improve it?
> >
> > Add -q:v 1 to your command line. The number does specify the compression ratio. 0 ist best quality and 9 is highest compression.
> This is (nearly) completely wrong:
> 9 is still high quality, highest compression happens at a much higher value.
> Old MEncoder documentation recommends not use a value lower than 2, sane values start between 5 and 10.
> To Flavio:
> The answer to your question depends on your use case: Setting a constant quantiser as suggested leads to output more similar to constant quality as is possible with x264 (and newer encoders) and is likely a good idea nowadays, the alternative is setting a bitrate, this should be combined with two-pass encoding and leads to the best quality - file size relation (which should be less relevant if you don’t write to a CD).
> Carl Eugen
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