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Greeting from S. Korea !
I am parsing the output of ffmpeg with perl. Particular, I want to print only
these lines among the output and capturing the resolution, i.e. 1280x720.
....
Stream #0:0: Video: h264 (High), yuv420p, 1280x720, SAR 1:1 DAR 16:9, 23.98
fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
Stream #0:1(jpn): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s (default)
Stream #0:2(eng): Subtitle: ass (default)
.....
My code is following:
# INFO is pipe to ffmpeg
# Here, the <print "$1 $2 $3 $4\n"> is for debugging .
while ( <INFO> ) {
if ( <regular expression> ) {
print "$1 $2 $3 $4\n";
}
}
Desirable outputs:
-> Video 1280 720
Audio
Subtitle
Regarding the <regular expession>:
1. /Stream #\d:\d.*(Video|Audio|Subtitle).*(\d+)x(\d+)/ (greedy)
-> Video 0 720
Q: why does $2 give 0? I remember .* match backward starting from the end of
the string. Then it should be "Video 1280 720" as output.
2. /Stream #\d:\d.*(Video|Audio|Subtitle).*?(\d+)x(\d+)/ (non greedy)
-> Video 1280 720
Q: I can understand this, but again I think (1) should work too.
3. /Stream #\d:\d.*(Video|Audio|Subtitle).*?(?:(\d+)x(\d+))?/ ( non-capturing
optional group )
-> Video
Audio
Subtitle
Q: It seems that the resolution part is ignored because it is optional.
Otherwise, the output will contains "Video" only as (1) and (2). How can I
circumvent this ?
4. /Stream #\d:\d.*(Video|Audio|Subtitle).+?(?:(\d+)x(\d+))?.*?$/
-> Video
Audio
Subtitle
Q: I tried to match things after the resolution, hoping that it will be
captured.
5. /Stream #\d:\d.*(Video|Audio|Subtitle).+?(?:(\d+)x(\d+))?(.*?)$/ ( let's
capture the last part)
-> Video h264 (High), yuv420p, 1280x720, SAR 1:1 DAR 16:9, 23.98 fps, 23.98
tbr, 1k tbn, 47.95 tbc (default)
Audio ac3, 48000 Hz, stereo, fltp, 192 kb/s (default)
Subtitle ass (default)
Q: Now $2 and $3 is undef, and the rest of the string went to $4. Again, I am
quite puzzled by the output.
Please pardon my long email. I hope someone can point out the flaws in my
logic. Here, I can match and print Video/Audio/Subtitle separately.
But I wish for one expression to match them all, one expression to print them.
Best regards,
Viet-Duc
