[FFmpeg-devel] Query regarding codec parsers

[Carl Eugen Hoyos]

Am So., 29. März 2020 um 14:23 Uhr schrieb Gautam Ramakrishnan
<gautamramk at gmail.com>:

> I had gone through ticket #7445

Better tickets are imo:
https://trac.ffmpeg.org/ticket/4669
https://trac.ffmpeg.org/ticket/4679
sample in http://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket4679/
https://trac.ffmpeg.org/ticket/4827
https://trac.ffmpeg.org/ticket/5360

Two of them look easy to fix, the difficulty could be to explain
why your fix is correct (in the commit message).

> and it mentions about JPEG2000 parser.
> What exactly does a parser do and how is it different from a decoder?
> I am unable to understand the exact use case of a parser.

Try the following:
$ cat 1.jpg 2.jpg | ffmpeg -i -f null -
(Is expected to decode two frames as can be seen in the console output,
also works for example with png)

$ cat 1.j2k 2.j2k | ffmpeg -i - -f null -
Will only decode one frame because there is no parser to split the
input.

Carl Eugen