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

[Carl Eugen Hoyos]

> 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