[Ffmpeg-devel-irc] ffmpeg.log.20170617

burek burek021 at gmail.com
Sun Jun 18 03:05:01 EEST 2017

[01:19:32 CEST] <postmodern> looking for documentation for various stereo3d settings. trying to combine two webcams into one stereoscopic video. i tried using sbs2l:arcg, but this gives me a portrait sized video, and it seems to favor one webcam over the other.
[02:12:25 CEST] <postmodern> ah found the stereo3d documentation. hmm i think i need to somehow combine the two video streams side-by-side then put them through stereo3d
[02:27:25 CEST] <postmodern> hmm think i got it working, but getting low fps and "past duration too large" warnings
[09:11:09 CEST] <johnjay> hmm
[09:11:26 CEST] <johnjay> furq is it bad if when running apt-get upgrade I get an error about unmet dependencies?
[12:37:52 CEST] <ChocolateArmpits> Is it possible to use overlay filter or any other filter to have any of the two inputs continue to be output when one of them dies/goes offline ?
[12:38:30 CEST] <ChocolateArmpits> Currently overlay only halts the encoding until the one of the inputs is online again
[13:47:49 CEST] <noble> hi all, I had some issues with m3u8 downloading using Ffmpeg, i've since come up with a workaround but I was wondering where the best place to report this is so it can be included in the code? Thanks
[14:49:10 CEST] <dongs> dong-around
[17:16:43 CEST] <ArsenArsen> What options and how do I set on my AVCodecContext to set H264 CRF and preset?
[17:42:35 CEST] <DHE> ArsenArsen: when in doubt, you can specify (almost) all ffmpeg command-line args with an AVDictionary. like:  av_dict_set(&dictptr, "crf", "21", 0);
[17:44:18 CEST] <DHE> which is good because after checking that's necessary for x264
[17:51:13 CEST] <ArsenArsen> So, DHE, arguments equate to dict. variables?
[17:53:03 CEST] <DHE> yes. it's intended to allow codec and format specific options but you can specify standard options this way as well
[17:53:39 CEST] <ArsenArsen> I see, and I assume Id use `av_opt_set(out->enc->priv_data, <key>, <val>, 0);` to set it?
[17:53:57 CEST] <ArsenArsen> I mean, I could use
[17:54:23 CEST] <DHE> -f "/mnt/yeti/$package-$id-$name/1080p.m3u8"
[17:54:26 CEST] <DHE> oh shit..
[17:54:29 CEST] <DHE> http://ffmpeg.org/doxygen/trunk/group__lavu__dict.html#ga8d9c2de72b310cef8e6a28c9cd3acbbe
[17:54:33 CEST] <DHE> that's the wrong clipboard buffer...
[17:54:40 CEST] <ArsenArsen> xD
[17:55:12 CEST] <ArsenArsen> Alright, thank you!
[17:55:43 CEST] <ArsenArsen> I assume something like 1K would work for variable bitrate
[17:56:12 CEST] <DHE> also, http://ffmpeg.org/doxygen/trunk/libavcodec_2options__table_8h_source.html here's the table of "generic" fields accepted by dictionaries for AVCodecContext
[17:56:31 CEST] <DHE> for the generics it's also a good way to look up what fields in an AVCodecContext they correspond to
[17:58:22 CEST] <ArsenArsen> I'm yet to use dictionaries :)
[18:23:57 CEST] <m712> hello
[18:24:21 CEST] <m712> it seems like ffmpeg does not insert keyframes when i convert a video to vp9...
[18:24:31 CEST] <m712> how can I add keyframes to the output video?
[18:25:16 CEST] <kerio> -g
[18:25:48 CEST] <m712> i cannot find it documented anywhere, how do I use it?
[18:27:54 CEST] <ChocolateArmpits> write a number after that matches  the gop length you're after
[18:28:06 CEST] <m712> gop length?
[18:28:27 CEST] <ChocolateArmpits> each gop starts with a keyframe
[18:28:39 CEST] <ChocolateArmpits> so using that you also define the keyframe rate
[18:32:54 CEST] <m712> ChocolateArmpits: sorry, i do not know what a "gop" is, can you please give me documentation/tell me what it is?
[18:33:50 CEST] <ChocolateArmpits> it's a "group of pictures", a coding method used to cut down on repeating visual portions over a time period
[18:34:21 CEST] <m712> i see
[18:34:43 CEST] <m712> so -gop 30 means i get a keyframe every 30 "group of pictures" i.e. fames?
[18:34:46 CEST] <m712> frames*
[18:34:57 CEST] <ChocolateArmpits> yes
[18:35:00 CEST] <m712> or rather a gop starts every 30 frames
[18:35:05 CEST] <m712> i see
[18:35:07 CEST] <m712> thank you
[18:35:28 CEST] <ChocolateArmpits> There are several types of frames that are coded in a gop, one of them is I-frames also called keyframes (a term taken from animation)
[18:35:38 CEST] <kerio> does a gop *have* to start with a keyframe?
[18:35:42 CEST] <m712> what -g value would be appropiate for an 50fps video?
[18:35:50 CEST] <m712> i was thinking 50 or 100
[18:35:53 CEST] <kerio> m712: it depends on what you use for streaming
[18:36:15 CEST] <ChocolateArmpits> a 2 second gop is most optimal
[18:36:15 CEST] <m712> it will be viewed via the browser's default video viewer
[18:36:33 CEST] <ChocolateArmpits> Longer gops add latency on playback end
[18:37:49 CEST] <m712> i see
[18:38:07 CEST] <kerio> never keyframes
[18:38:13 CEST] <kerio> intra frame refresh is all you need \o/
[19:26:12 CEST] <buko1911> hey guys, is there a way to increase the attenuation of the lowpass filter ?
[19:52:52 CEST] <c3-Win> buko1911: https://ffmpeg.org/ffmpeg-filters.html#lowpass
[20:20:54 CEST] <styler2go> Let's say i have a .txt file with some text in each line, can i somehow create a video file which shows one line per one second?
[20:28:35 CEST] <ChocolateArmpits> styler2go, look into drawtext filter
[20:32:05 CEST] <kerio> styler2go: produce a sequence of images and encode them with ffmpeg maybe?
[20:33:00 CEST] <styler2go> hmm good idea, i could generate one picture for each second
[20:33:47 CEST] <furq> you probably just want to convert that to an srt and use the subtitles filter
[20:34:23 CEST] <styler2go> I wa sjust looking into the .srt option but i thought the image idea is faster
[20:34:44 CEST] <furq> i doubt it
[20:42:09 CEST] <rigid> ahoy
[20:42:51 CEST] <rigid> i'm trying to compile 3.3.2 with vidstab support, but I _think_ the pkg-config autoconf macro is somehow fubar
[20:43:09 CEST] <rigid> config.log https://gist.github.com/4fc604c76f9393c1d866e4c3e1d07c0b
[20:43:45 CEST] <rigid> when I run pkg-config manually, it works fine. Plus the log doesn't show quotes around the pkg-config argument. Could that be an issue?
[20:54:24 CEST] <styler2go> furq: I am trying with subtitle now, the command i am using is: ffmpeg -f lavfi -i color=color=green:s=1920x1080:r=60 -c:v h264_nvenc -vf subtitles=out.srt eow.mp4 How does ffmpeg know when to stop? do i need to tell it or is the end of subtitle file enough?
[20:55:05 CEST] <rigid> nvm, i just found out it's a lib32 <-> lib64 issue
[20:55:12 CEST] <rigid> o/
[21:01:51 CEST] <styler2go> It doesn't show any subtitle
[00:00:00 CEST] --- Sun Jun 18 2017

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