[Ffmpeg-devel-irc] ffmpeg.log.20200126

[burek]

[03:26:23 CET] <unixabg> Greetings, I am wanting to capture 2 or 3 fps with snapshots from an rtsp feed, I am trying something like:
[03:26:32 CET] <unixabg> fmpeg -rtsp_transport tcp -i rtsp://blahblah -vf fps=fps=1/0.8 -strftime 1 %s-%04d.jpg
[03:28:31 CET] <unixabg> but I only appear to be getting 1 fps. How can I snapshot 2 or 3 frames per second with a jpeg for each frame?
[07:40:21 CET] <f00lest> How can I record my desktop audio using ffmpeg
[07:41:04 CET] <f00lest> tried `ffmpeg -f alsa -i hw:0 -t 30 out.wav `
[07:41:17 CET] <f00lest> got `Unknown input format: 'alsa' `
[07:43:13 CET] <f00lest> I've also tried installing `sudo dnf install alsa-lib-devel`
[07:43:19 CET] <f00lest> but still issue persists
[16:42:14 CET] <LFSVeteran> can't figure out why frame_size is 0, everywhere I check it's zero
[19:32:59 CET] <LFSVeteran> https://pastebin.com/L4UZfqHg
[19:33:18 CET] <LFSVeteran> seems like trouble starts at opening the input
[20:35:00 CET] <DHE> LFSVeteran: frame size of 0 means input size doesn't matter. sample_rate is samples per second, not bit rate or total samples (ie. 2 channel vs 1 doesn't mean double the sample_rate)
[20:37:14 CET] <LFSVeteran> ffmpeg -f s32le -ac 2 -ar 192000 -i http://ip:port/stream -acodec pcm_s32le output.wav
[20:37:35 CET] <LFSVeteran> sample_rate should be 192000 here?
[20:38:08 CET] <LFSVeteran> and channels 2?
[20:41:36 CET] <DHE> typically. but 192 kHz audio is pretty high. 96k is normally the highest I see
[21:03:40 CET] <LFSVeteran> the problem is that frame_size is 0 and therefore the number of samples is 0 and allocate will fail
[21:12:21 CET] <DHE> but it means there's no size requirement. so you can deliver samples as you have them rather than queuing and partitioning like you would need to do for AAC or such
[21:14:32 CET] <LFSVeteran> My knowledge with the FFmpeg api is very limited....The resampler can be removed too but how to fix this in the example....
[21:27:29 CET] <LFSVeteran> but if the input framesize doesn't matter, why is the output framesize 0?
[21:42:10 CET] <chaosblade> oh, lovely. managed to compile a static ffmpeg and libs with dynamic glibc (with the workaround in https://trac.ffmpeg.org/ticket/6431#comment:7).. only to find out something in my combo/libs needs libmvec that is glib 2.22 and up. CentOS/RHEL 7.x is on glibc 2.17 :X
[21:42:38 CET] <chaosblade> i wonder if just compiling on an older distro and/or with older glibc would work, but i imagine whatever needs mvec will complain
[21:42:52 CET] <chaosblade> probably the nvidia support i included
[21:43:23 CET] <chaosblade> maybe should also try cehoyos's suggestion for musl instead.
[21:43:27 CET] <DHE> chaosblade: https://github.com/wheybags/glibc_version_header  you may be interested in this then...
[21:44:29 CET] <chaosblade> Hm. That's an interesting read. Thanks for the heads up!
[21:45:44 CET] <cehoyos> chaosblade: I tested musl after suggesting it to you and it passes fate with current FFmpeg, should have a performance advantage
[21:45:44 CET] <kepstin> that's an openmp support library i think? if you compile whatever is using it with an older gcc/glibc it'll probably just not use it (and the resulting code might be slower)
[21:46:16 CET] <chaosblade> kepstin, yeah, that was what i was thinking.
[21:46:37 CET] <cehoyos> This is of course you don't need to many dependencies which may also make compilation with glibc less troublesome
[21:48:27 CET] <chaosblade> might be worth a try. was it just a ./configure level change or anything more special?
[00:00:00 CET] --- Mon Jan 27 2020