On 2/27/2021 12:23 AM, Carl Eugen Hoyos wrote:
ffmpeg -f lavfi -i testsrc=duration=5:size=1280x720:rate=30000/1001
testsrc.mpg
Just for completeness:
This does not create a MPEG-2 program stream but an MPEG-1 system stream.
No doubt that's correct, although maybe unexpected by many people.
(this is mostly to document things so it can found in the list archive)
ffmpeg-all doc tells us
-f fmt (input/output)
Force input or output file format. The format is normally auto detected
for input files and guessed from the file extension for output files,[...]
but there is nothing that explains which guesses are made (and how) on the
output format. Most should be fairly obvious (e.g. .ogg or .wav); the
confusion comes when you get to all of the MPEG-related formats (vob, dvd,
mp2, mp4, etc), all of which -might- be found in a file called .mpg (right
or wrong, it happens).
ffmpeg -muxers will show a list of muxers and what appear to be their
default file extensions (although .mpg isn't shown, .mpeg is; it's
reasonable to treat them as same).
Note also that this identifies the -container-, not necessarily the codec or
other parameters. For instance- nothing specifically mentions the difference
between the MPEG-2 PS in .vob vs .dvd. This is similar to the -target
option, the doc page doesn't mention all of the parameters that are being
set (it's only in the code).
(It appears that the work starts with av_guess_format() calling
av_muxer_iterate() which then looks over the list of all muxers (in
muxer_list.c) and appears to check each one in turn to see what it thinks of
the file name/extension/mime-type passed. When time permits, I may dive more
deeply into this.)
Later,
z!
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