[Ffmpeg-devel-irc] ffmpeg.log.20191026

[burek]

[02:20:22 CEST] <whitestone> hello
[09:13:39 CEST] <JAK-Zero> hey, I'm trying to find out the exact settings that the -preset options apply for x264
[09:14:16 CEST] <JAK-Zero> I tried `ffmpeg -h encoder=libx264` and it said `-preset            <string>     E..V..... Set the encoding preset (cf. x264 --fullhelp) (default "medium")`
[09:14:32 CEST] <JAK-Zero> what does `cf. x264 --fullhelp` mean?
[09:14:58 CEST] <Lypheo> JAK-Zero: see here: http://x264.janhum.alfahosting.org/fullhelp.txt
[09:17:04 CEST] <JAK-Zero> oh thanks
[09:17:18 CEST] <JAK-Zero> huh, they don't set crf?
[09:17:46 CEST] <JAK-Zero> it doesn't look like it sets bitrate either
[09:19:11 CEST] <Lypheo> why would they? it should be clear from the naming that the presets are meant to control speed, not quality
[09:20:13 CEST] <Lypheo> (although they do have bearing on quality to some extent at a fixed CRF)
[09:20:15 CEST] <JAK-Zero> oh, I thought you were picking compromises between speed and quality
[09:20:41 CEST] <JAK-Zero> what's the downside of picking ultrafast then?
[09:20:59 CEST] <Lypheo> terrible compression
[09:21:12 CEST] <Lypheo> meaning bloated file size
[09:21:29 CEST] <JAK-Zero> oh ok
[09:23:44 CEST] <JAK-Zero> I think I understand now, thanks for the help
[09:29:21 CEST] <Reinhilde> I have a progressive drop in recording framerate as the hours rack up.
[14:52:57 CEST] <pbox> hi I'm using ffmpeg to stream from a VPS to youtube and twitch. the audio plays fine - using jack as source - but I tried to use x11grab for streaming the desktop and it only shows a black screen
[14:53:56 CEST] <durandal_1707> use yuv420p format for output
[14:54:25 CEST] <pbox> I did
[14:55:05 CEST] <cehoyos> Does it work if you write to a local file?
[14:55:15 CEST] <BtbN> x11grab on a VPS?
[14:55:21 CEST] <pbox> in the -pix_fmt argument?
[14:55:27 CEST] <pbox> BtbN: I have lxqt installed
[14:55:36 CEST] <BtbN> Does the thing even have any kind of GPU?
[14:55:44 CEST] <pbox> and can use vnc just fine. no it does not
[15:02:52 CEST] <pbox> same thing happens when I write to disk
[15:04:09 CEST] <pbox> BtbN: do you think I won't get it to work without a GPU?
[15:04:27 CEST] <BtbN> maybe with full software framebuffer and rendering, but it will perform horribly
[15:14:32 CEST] <pbox> BtbN: thanks. I'm trying to search how to set ffmpeg to use software framebuffer and rendering but can't seem to find anything online. I don't mind a horrible performance if I can get some visuals for now. is it very hard?
[15:24:15 CEST] <asdjklnaskjdfgh> is there a way to list the codecs supported by a muxer?
[15:25:58 CEST] <durandal_1707> nope
[15:26:25 CEST] <asdjklnaskjdfgh> is there a reason for that?
[15:26:33 CEST] <durandal_1707> yes
[15:28:56 CEST] <asdjklnaskjdfgh> is there any way to see what combinations are possible?
[15:29:09 CEST] <cehoyos> What muxer are you interested in?
[15:29:36 CEST] <asdjklnaskjdfgh> I just want to write a little interface, where you can select a muxer and the codecs
[15:29:37 CEST] <cehoyos> Some support any codec, some are very limited
[15:29:49 CEST] <cehoyos> This is currently not easily possible.
[15:30:31 CEST] <cehoyos> Feel free to check AVOutputFormat.codec_tag but it does not always help
[17:13:23 CEST] <asdjklnaskjdfgh> Why does ffprobe show on some videos duration N/A, but when I open it manually it shows it under metadata?
[17:16:56 CEST] <cehoyos> Command line and complete, uncut console output missing (I guess the metadata is ignored)
[17:17:19 CEST] <asdjklnaskjdfgh> -v error -select_streams v:0 -show_entries stream=width,height,avg_frame_rate,duration -of default=noprint_wrappers=1:nokey=1
[17:27:26 CEST] <asdjklnaskjdfgh> this works ffprobe -v quiet -print_format json -show_format -show_streams
[00:00:00 CEST] --- Sun Oct 27 2019