[Ffmpeg-devel-irc] ffmpeg.log.20191229

[burek]

[02:28:56 CET] <sine0> how can i record an audio stream in ffmpeg. Im thinking some kind of curl/wget pipe stdin thingy to ffmpeg.
[02:48:37 CET] <nicolas17> sine0: ffmpeg can take HTTP URLs as input, no need for curl
[03:23:38 CET] <DHE> it can even take HTTPS if openssl or gnutls was available at build time
[04:50:40 CET] <Hello71> muh libressl
[16:40:32 CET] <M6HZ> Hello, I'm trying to test the hardware acceleration of h264 encoding with h264_vaapi, but I get this error: Impossible to convert between the formats supported by the filter 'Parsed_null_0' and the filter 'auto-inserted scaler 0'
[16:42:36 CET] <M6HZ> Do you know what I should do?
[16:50:00 CET] <ddubya> what is the best command line to get a 0 exit status and only probe the streams? .e.g ffmpeg -to 0.01 -i <input> -f null dummy
[16:50:28 CET] <ddubya> *without using ffprobe*
[16:50:48 CET] <pink_mist> I was about to suggest using ffprobe ...
[16:50:57 CET] <pink_mist> why don't you want to use ffprobe??
[16:57:47 CET] <ddubya> I'm doing an ffmpeg gui, I only want to require ffmpeg.exe
[17:05:42 CET] <DHE> you have to be careful that a fully named "dummy" doesn't actually exist though... or add -y to that command
[17:24:41 CET] <ddubya> DHE, good point, turns out "-f null" will not touch the output file
[17:48:38 CET] <voices> hey, are there any good resources about using ffmpeg for HLS?
[18:06:46 CET] <DHE> depends on your goal. there are a few different ways to do HLS... realtime vs VOD,  and single vs multi bitrate
[18:06:53 CET] <M6HZ> I still haven't solved my problem, does anybody have any idea?
[18:26:34 CET] <voices> DHE: basically i want to automate converting .mkv files to 720p, have them retain their original aspect ratio, and output .ts segments
[18:28:39 CET] <voices> so i think that's video on demand
[18:39:29 CET] <DHE> voices: yeah that sounds right. so most likely you want: ffmpeg -i input.mkv -c:a aac -b:a 128k -ac 2 -vf scale=-2:720 [H264 options go here] -hls_time 8 -hls_list_size 0 -f hls output.m3u8
[18:39:53 CET] <DHE> hls_time is the duration of the .ts files, and what's important is selecting your keyframe interval (the -g parameter) to be suitable for the number given
[18:43:54 CET] <voices> DHE: thanks. are you sure it's 2:720 ? i thought it was 1:720.
[18:44:50 CET] <DHE> voices: the absolute value of the negative number indicates the multiple required. -2 means an even number must be selected for this value (because H264 in yuv420 requires it)
[18:45:32 CET] <DHE> -1 will give the most correct calculation, but -2 is required for 4:2:0 colourspace
[18:46:47 CET] <voices> DHE: right, yeah that was a confusing part of it. because the segment sizes vary, like so https://i.imgur.com/VykgUOB.png
[18:46:50 CET] <voices> oh ok
[18:47:04 CET] Action: voices reads up on 4:2:0 colourspace
[18:47:32 CET] <DHE> voices: https://en.wikipedia.org/wiki/Chroma_subsampling#Sampling_systems_and_ratios  pictures help
[18:50:41 CET] <voices> DHE: cool. it sounds like i don't have a choice anyway
[18:51:58 CET] <DHE> basically yeah. h264 supports 4:4:4 but you can't rely on players to be able to handle it
[18:55:01 CET] <voices> DHE: oh, right. i think i read about that now you mention it. how does it know what size to make each segment? i expected each segment to be the same size but they're all different. and different videos, seem to be differetn again. for instance one video was divided into 19 segments, and no segment was greater than 2.5MB, but as you can see in the image i posted, those segments are around 5.0B
[18:56:03 CET] <DHE> file size will vary with bitrate on a second-by-second basis, but if the durations are variable then you need to lock down you keyframe interval.
[18:56:46 CET] <DHE> with libx264 you can use -x264-params no-scenecut to force exact keyframe pacing
[18:56:57 CET] <voices> haha are you just making up words now? just kidding
[19:19:03 CET] <voices> DHE i think the durations are the same anyway. thanks for your help. anything else i ought to know?
[19:21:53 CET] <DHE> ideally you want a constrained max bitrate so that the bitrate doesn't spike up too high. HLS is designed for streaming so you should know what the max bitrate is if it's going on bandwidth constrained environments like the internet
[19:22:06 CET] <DHE> if this is some kind of home LAN thing it probably doesn't matter
[20:01:33 CET] <voices> DHE: so what are thew h264 options i'll need
[20:03:15 CET] <DHE> unless you have specific requirements, something like: -profile:v high -crf 25 -maxrate:v 8M   # adjust numbers to your needs
[20:05:19 CET] <voices> DHE: i'll give it a whirl. appreciate ya
[20:30:26 CET] <analogical> how do I tell ffmpeg to use a certain bitrate when I encode aac ?
[20:31:36 CET] <relaxed> -c:a aac -b:a 192k
[20:33:49 CET] <analogical> relaxed, Thanks. FFmpeg is a great tool but it has the worst documentation in the history of software.
[20:34:31 CET] <relaxed> https://trac.ffmpeg.org/  and https://trac.ffmpeg.org/wiki/Encode/AAC
[20:37:20 CET] <relaxed> once you get the hang of using basic commands the documentation is easier to search/read
[20:37:53 CET] <analogical> I've been reading this https://ffmpeg.org/documentation.html and it's a nightmare
[20:43:32 CET] <durandal_1707> analogical: stop shitting about documenation
[20:44:39 CET] <relaxed> Yeah, they're man pages converted to web pages. I recommend focusing on the wiki and reading actual man pages when needed, also "ffmpeg -h full | less"
[20:57:07 CET] <furq> you must not have used very much software
[20:58:34 CET] <furq> the only major gripe i have with the docs is generic lavc options not having defaults/ranges documented per-codec
[20:59:00 CET] <furq> and maybe some formats/codecs being missing from the web docs, although they're covered fine by -h
[20:59:07 CET] <furq> web docs/manpages
[20:59:38 CET] <furq> i'd say that's pretty good considering how colossal ffmpeg is
[21:38:56 CET] <FLXX> hi
[21:41:05 CET] <FLXX> can one help me with cropping please?
[21:41:39 CET] <FLXX> I have a video that is has horizontally 2 black rects besides.
[21:41:50 CET] <FLXX> and I want to crop them away
[21:42:38 CET] <FLXX> I have 720x1280 in original
[21:42:41 CET] <FLXX> and "D:\FFMPEG\ffmpeg.exe" -i "G:\3.mp4" -filter:v "crop=480:1280:0:1280" -c:a copy "G:\vivi\Tout.mp4"
[21:42:45 CET] <FLXX> as commadline
[21:43:09 CET] <FLXX> but anyhow it only gets squeezed horizontally and smaller
[21:56:54 CET] <M6HZ> I'm trying to test the hardware acceleration of h264 encoding with h264_vaapi, but I get this error: Impossible to convert between the formats supported by the filter 'Parsed_null_0' and the filter 'auto-inserted scaler 0'
[22:14:56 CET] <rascal999> hello I have mkvs which I've tried to convert using -codec copy to mp4s for playback in browser
[22:16:03 CET] <rascal999> when trying to play resulting file in browser, audio doesn't work or video doesn't, what command do i need to convert (lossless as possible) and always work in browser?
[22:17:18 CET] <pink_mist> depends. if the video and/or audio codec is something your browser supports and mp4 supports it too, copy is the best option
[22:17:33 CET] <void09> any way to pass custom encoder parameters that are not available by default with ffmpeg ?
[22:17:40 CET] <pink_mist> if it isn't, find what your browser does support, and use the best encoding options for that codec
[00:00:00 CET] --- Mon Dec 30 2019