On 04-05-2019 06:42 PM, Nicolas George wrote:
Gyan (12019-05-02):
The flow is
avformat_write_header -> avformat_init_output -> init_muxer
And in the last function, lines 293-385 (as of 7eba26451) carry out the
checks, and which my patch skips.
I missed this. My bad.
The problem is that there is no clean set of flags which isolate the
parameter-agnostic muxers - not surprising as this is a library for making
valid media files. A new flag could be invented, if the present patch is too
idiosyncratic. On a related note, as I mentioned elsewhere in this thread,
an existing flag AVFMT_NOTIMESTAMPS, which in theory I could use, is of no
help here, as it has been set for muxers which do handle timestamps in some
way.
Yet, the name test is wrong: there are other muxers that absolutely do
not care about timestamps, or any other kind of parameters. The null
muxer, for starter.
I see a few options to make this work properly:
- Add an option "-noout" for ffmpeg to let it run without output, until
the end of inputs. This would be useful for other situations,
including cases when the log from filters is what the user is
interested in. It would replace "-f null -" that we always use.
- Add an option "-mux_params_check 0" for ffmpeg output streams, tu
allow skipping these tests explicitly. Your use case is specific
enough that an additional option is acceptable.
- Create the required flags to mark muxers that do not require these
tests.
I think what I would prefer is a combination of 2 and 3. Mark muxers
which don't need checks but add an option to actually disable checks. 2
alone can produce invalid files if used with a regular muxer. At
minimum, a warning should be issued. 3 alone has no flexibility.
If acceptable, I'll revise the patch that way.
Thanks,
Gyan
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