[Ffmpeg-devel-irc] ffmpeg.log.20180812

burek burek021 at gmail.com
Mon Aug 13 03:05:01 EEST 2018

[02:59:18 CEST] <TheAMM> Is there any way to check which libopus version ffmpeg was built with?
[03:02:48 CEST] <furq> not if it's a static binary
[04:07:59 CEST] <Hello71> TheAMM, furq: actually it is possible even in static binary if the binary was not compiled with -flto or -Wl,--gc-sections
[04:09:10 CEST] <Hello71> I assume that the celt.c file is always compiled in
[04:09:18 CEST] <Hello71> so just run the opus_get_version_string function
[04:09:27 CEST] <Hello71> or disassemble it and read the referenced string
[04:10:09 CEST] <Hello71> or better yet just run grep -ao 'libopus [A-Za-z0-9_.\-]*' ffmpeg
[04:10:16 CEST] <TheAMM> Yeah that goes a bit above telling the guy to just download a fresh static ffmpeg
[04:10:35 CEST] <Hello71> if you turned on lto then you're SOL though
[04:10:49 CEST] <Hello71> unless you feel like manually comparing the lists of symbols, which isn't even reliable with LTO
[04:11:00 CEST] <TheAMM> He just wanted to know if he has opus 1.2
[04:11:36 CEST] <TheAMM> I wondered if I had missed some -library_versions or such
[04:14:10 CEST] <Hello71> no
[04:14:18 CEST] <Hello71> grep opus_get_version_string ffmpeg
[04:14:28 CEST] <Hello71> although I guess it could be compiled in
[04:14:41 CEST] <Hello71> grep -ao 'libopus [A-Za-z0-9_.\-]*' dynamic-ffmpeg
[13:33:02 CEST] <pi--> https://paste.pound-python.org/show/aFfv6HOQ104C924qckb2/ <-- could anyone help me understand what this code is doing?
[13:33:21 CEST] <pi--> Or rather, I know that it is in setting black at the beginning of the video. But how is it doing it?
[13:33:27 CEST] <pi--> Is the approach sensible?
[13:40:26 CEST] <pi--> `trim=0:$BLACK_S,geq=0:128:128` <-- What's geq doing?
[13:40:39 CEST] <TheAMM> Egh.
[13:41:05 CEST] <TheAMM> It's reading the input file, trimming it to the given duration and filtering it to black
[13:41:34 CEST] <TheAMM> (it also converts the timebase to be 600fps if I understand video_track_timescale correctly)
[13:41:43 CEST] <pi--> https://ffmpeg.org/ffmpeg-filters.html#geq doesn't seem to document '3 params'
[13:42:03 CEST] <TheAMM> lum, cb, r
[13:42:06 CEST] <TheAMM> The first three
[13:42:47 CEST] <TheAMM> It may be sane if you want to preserve the variable framerate timestamps
[13:44:36 CEST] <pi--> I generated the source video by splitting it into A&V streams.
[13:45:10 CEST] <TheAMM> Is the framerate constant or variable?
[13:45:16 CEST] <pi--> I don't know if this is going to cause an issue with timestamps.
[13:45:29 CEST] <pi--> Constant, I think...
[13:45:41 CEST] <TheAMM> Where does the video come from?
[13:45:52 CEST] <pi--> i.e. the in-video is the output of previous ffmpeg operation
[13:46:20 CEST] <TheAMM> ffmpeg doesn't implicitly make the framerate constant
[13:46:49 CEST] <TheAMM> Things depend on things
[13:47:30 CEST] <TheAMM> If your video is CFR and it's okay to use CFR, that simplifies things (and makes them faster since you don't have to generate two temporary files just to merge them)
[13:56:07 CEST] Action: pi-- bbl
[13:56:08 CEST] <pi--> tx TheAMM
[13:56:31 CEST] <TheAMM> k
[18:16:44 CEST] <pi--> https://paste.pound-python.org/show/aFfv6HOQ104C924qckb2/ <-- I'm revisiting this, looking at `-vf trim=0:$BLACK_S,geq=0:128:128`
[18:16:59 CEST] <pi--> Could someone explain the last three numbers?
[18:17:13 CEST] <pi--> I can't see from the documentation what they signify.
[18:18:13 CEST] <pi--> https://ffmpeg.org/ffmpeg-filters.html#geq
[18:19:13 CEST] <pi--> So lum, chrominance-blue, chrominance-red ???
[18:19:39 CEST] <pi--> Why would we need anything beyond the first `lum=0`?
[20:05:49 CEST] <kepstin> pi--: the colour you get with Y=0, Cb=0, Cr=0 is dark green. Need to set Cb and Cr to neutral to get black.
[23:54:16 CEST] <Obliterous> got a compile/configure question, if someone is available to assist.
[23:56:58 CEST] <Cracki> you need to make the first move. pastebin or upload EVERYTHING you have. nobody's gonna commit, especially if you make it like pulling teeth.
[23:58:05 CEST] <Obliterous> reasonable enough. just wanted to make sure someone was awake in here first. :-)
[23:58:39 CEST] <Cracki> I'm neither awake nor in here nor knowledgeable
[23:58:55 CEST] <Cracki> just trying to keep you from shooting your own foot
[00:00:00 CEST] --- Mon Aug 13 2018

More information about the Ffmpeg-devel-irc mailing list