[Ffmpeg-devel-irc] ffmpeg.log.20181222

[burek]

[03:37:04 CET] <utack> how does one do subtraction for the select filter?
[03:37:14 CET] <utack> i want frame number n minus a fixed number
[03:39:06 CET] <kepstin> utack: you can use the - operator to do subtraction as you'd normally expect...
[03:39:17 CET] <kepstin> utack: see also the expression reference here: https://www.ffmpeg.org/ffmpeg-utils.html#Expression-Evaluation
[03:39:28 CET] <utack> okay odd, thanks
[03:42:22 CET] <utack> the "\," is to escape comma?
[03:44:13 CET] <kepstin> yeah, but note that you might also have to escape the \ so that your shell doesn't interpret it (or put the expression into single quotes)
[03:45:25 CET] <kepstin> (a useful trick is to run `echo -vf select=yourexpression` and make sure all the \ and , are in the right spot)
[03:58:27 CET] <utack> works now, thanks for the help
[04:14:22 CET] <crankharder> I want to process some large 4K footage to 'thumbnail' size -- e.g. aggressively compressed to save massive amounts of space, but i can still view it to get a sense for whats in the footage -- this seems to work decently well, just wondering if there are any flags to make it faster/smaller/better.  thanks!
[04:14:28 CET] <crankharder> ffmpeg -i in.mp4 -c:a aac -q:a 1.0 -c:v libx264 -vf scale=320:240 out.mp4
[04:19:25 CET] <kepstin> crankharder: just general libx264 stuff - use the -preset option to make it slower/better, use the -crf option to make it smaller/worse
[04:20:09 CET] <kepstin> you can't get faster and smaller and better.
[04:20:24 CET] <kepstin> only pick 2
[04:22:57 CET] <kepstin> the usual recommendation for using libx264 encoder is to use the -preset option to pick the slowest preset you can stand, then use the -crf option to adjust between the size vs. quality tradeoff.
[04:23:21 CET] <kepstin> (you can use -preset to speed it up, too, the default is 'medium')
[04:26:03 CET] <kepstin> also, last I heard, it's better to specify a bitrate when using the builtin aac encoder (-b:a 128K or something) rather than use the -q:a option.
[04:32:56 CET] <crankharder> thanks for the tips!
[04:47:19 CET] <Hello71> note that because x264 is bad, you must not do it the other way around
[04:48:42 CET] <kepstin> well, it's not that x264 is bad, it's probably one of the best encoders around for any codec tbh.
[04:49:09 CET] <kepstin> it's just that the -crf option isn't truely a quality setting, it's rather a bitrate vs quality tradeoff setting that depends on a bunch of other settings
[04:49:21 CET] <kepstin> and changing preset changes a bunch of other settings
[04:49:54 CET] <kepstin> (crf was originally part of how 2-pass bitrate encoding worked, and you were expected to use (mostly) the same settings for both passes)
[07:26:13 CET] <cheapie> So I figured out how to get ffmpeg to produce files that Panasonic DVD players with "DivX" (not DIVX) support will play :)
[07:26:17 CET] <cheapie> "ffmpeg -i /path/to/source/file -c:v libxvid -c:a mp2 /path/to/destination/file.avi" seems to do the trick.
[10:48:34 CET] <pagios> hi all, ffmpeg -i rtmp://localhost/src/$name -o rtmp://localhost/src/stream2 <--- can i use this to convert stream1 to stream2?
[10:50:40 CET] <pagios> hello?
[10:51:33 CET] <pink_mist> be patient
[10:52:22 CET] <pink_mist> there might be someone who knows the answer to your question and is willing to give you an answer, but you'll need to wait for said person to show up
[10:52:27 CET] <pink_mist> I've got no clue
[12:28:18 CET] <ariyasu> pagios try
[12:28:37 CET] <ariyasu> ffmpeg -i rtmp://localhost/src/$name -c copy rtmp://localhost/src/stream2
[12:28:50 CET] <ariyasu> ffmpeg doesn't use -o to specify an output
[12:29:23 CET] <pagios> is ffmpeg better than libav and gstreamer?
[13:23:02 CET] <alone-x> hello any one can use qsv with ffmpeg under windows?
[14:30:16 CET] <Bear10> which methods should i be looking at to grab a packet and get a frame to generate a preview image?
[19:12:35 CET] <Alina-malina> I want to append a certain sound.mp3 to an existing video i mean basically i have a backgroundmusic.mp3 which is 00:10:00 duration and i need that on 07:15 to add a bass.mp3 file, but ti not lose the backgroundmusic.mp3, how to achieve this with ffmpeg?
[19:12:55 CET] <Alina-malina> and its a file.mp4 file that both tracks should be applied to
[19:14:38 CET] <ariyasu> you can concat them with ffmpeg
[19:14:50 CET] <ariyasu> or copy /b works with most audio files
[19:14:57 CET] <ariyasu> then use ffmpeg to mux them
[19:15:12 CET] <ariyasu> https://trac.ffmpeg.org/wiki/Concatenate
[19:15:43 CET] <ariyasu> or "copy /b audio1.mp3 + audio2.mp3 output.mp3"
[19:16:04 CET] <ariyasu> ffmpeg -i file.mp4 -i output.mp3 -c copy output.mp4
[19:16:10 CET] <ariyasu> somthing like that should work fine too
[19:17:10 CET] <Alina-malina> no not concat
[19:17:41 CET] <Alina-malina> i need to apply 2 tracks at the same time
[19:17:46 CET] <Alina-malina> not concatition
[19:17:51 CET] <Alina-malina> concatination
[19:18:03 CET] <furq> Alina-malina: -i bgm.mp3 -i sound.mp3 -lavfi "[0:v]atrim=end=7:15[tmp];[tmp][1:v]concat"
[19:18:14 CET] <furq> s/v/a/
[19:18:30 CET] <Alina-malina> hmmm let me try this thanks
[19:19:00 CET] <furq> that will just cut bgm.mp3 at 7:15 and play sound.mp3
[19:19:03 CET] <furq> i'm not sure if that's what you awnt
[19:19:13 CET] <Alina-malina> no not cut
[19:19:15 CET] <Alina-malina> append there
[19:19:25 CET] <Alina-malina> no need to interupt bgm.mp3
[19:19:35 CET] <Alina-malina> though its interesting effect hehe
[19:20:14 CET] <pink_mist> Alina-malina: append? but that's exactly what concatenation is
[19:20:24 CET] <pink_mist> and you didn't want concatenation
[19:20:26 CET] <c_14> sounds like you want adelay and amix
[19:20:28 CET] <pink_mist> you said so
[19:20:34 CET] <Alina-malina> c_14, yes
[19:20:47 CET] <Alina-malina> pink_mist, i need both files tp play at the same time pink_mist
[19:20:51 CET] <Alina-malina> to*
[19:21:11 CET] <furq> -lavfi "[1:a]adelay=435000|435000[tmp];[0:a][1:a]amix"
[19:21:21 CET] <Alina-malina> great great thanks
[19:21:28 CET] <furq> -lavfi "[1:a]adelay=435000|435000[tmp];[0:a][tmp]amix"
[20:28:31 CET] <Alina-malina> furq, Filter amix has an unconnected output  :-/
[20:32:28 CET] <durandal_1707> Alina-malina: you need to first learn basics
[20:42:03 CET] <Alina-malina> ok it worked
[20:42:05 CET] <Alina-malina> i figured it out
[20:42:55 CET] <Alina-malina> durandal_1707, no i think i need a good movie to watch now and relax, too much hard work already done today, enough working
[21:58:11 CET] <Alina-malina> furq, i am not sure, but what if i want to do the same, but more then 1 time? like 2 times or more? i tried to find this in documents, but it doesnt say anything about multiple amix and adelays in 1 command?
[00:00:00 CET] --- Sun Dec 23 2018