[Ffmpeg-devel-irc] ffmpeg.log.20170825

Sat Aug 26 03:05:01 EEST 2017

[00:07:02 CEST] <voip_> hello guys, i forgot what the normal range for q parameter ?
[00:08:14 CEST] <voip_> quantizer
[00:09:39 CEST] <kepstin> squarecircle: unless you've specifically asked ffmpeg to use a hw decoder, it won't be using one. You have to specify the device to use, so you can say which card to run on.
[00:09:46 CEST] <kepstin> voip_: depends on the codec.
[00:10:00 CEST] <voip_> actually acceptable value for CPU load  h264
[00:11:32 CEST] <kepstin> are you using the x264 encoder? If so, use the '-qp' option (not -q) for constant quantizer mode, and probably something around 20 or so, lower for higher quality.
[00:11:50 CEST] <squarecircle> kepstin: I'm not sure about that
[00:12:34 CEST] <kepstin> squarecircle: well, I'm sure about it ;)
[00:12:47 CEST] <squarecircle> kepstin: oh well, if I think, about it, yeah, a 1080p file creates 100% load on one cpu, a 4k  100% on four cpus
[00:12:51 CEST] <voip_> kepstin, i encoding 9 streams and have  q=32.0 in stats, but speed=0.992x
[00:13:11 CEST] <squarecircle> how do I can tell ffmpeg to use the hardware?
[00:13:32 CEST] <kepstin> voip_: the qp setting on x264 has rather minimal effect on how fast the encoder runs... look at the -preset option to adjust that.
[00:14:16 CEST] <kepstin> squarecircle: Neither of the machines you mentioned support hardware decoding...
[00:14:49 CEST] <kepstin> squarecircle: how to set it up depends on what type of hardware decoder you have and what OS.
[00:16:41 CEST] <voip_> kepstin, so quantizer stats doesnt related with CPU loading ? I was tink q shows how mmuch my CPU loaded
[00:16:59 CEST] <kepstin> voip_: nope, it's related to the visual quality of the encoded video
[00:17:14 CEST] <kepstin> (when using x264, it's a very loose relation, the numbers don't mean much)
[00:18:05 CEST] <kepstin> voip_: to make x264 run faster, use the -preset option to select a faster preset. The default is 'medium', so try 'fast', 'faster', 'veryfast', etc.
[00:20:00 CEST] <voip_> thank you, kepstin
[00:22:02 CEST] <squarecircle> kepstin: well I would put in some nvidia 8800GT that are moalding here
[00:22:42 CEST] <squarecircle> kepstin: iirc I can put in three cards
[00:23:25 CEST] <kepstin> squarecircle: 8800GT should be able to do 1080p h264 8bit decoding, but it doesn't have a hardware encoder.
[00:24:34 CEST] <kepstin> assuming you're using nvidia's drivers (do they even still support the 8800gt? Might need the legacy version), you can probably use the cuvid decoder as described here: https://trac.ffmpeg.org/wiki/HWAccelIntro#CUDACUVIDNvDecode
[00:24:47 CEST] <DHE> IIRC gtx680 or so was the first with the NVENC encoder chip on it
[00:25:32 CEST] <squarecircle> so hardware acceleration in ffmpeg does not uses the openCL or Cuda, but relies on available decoders?
[00:25:45 CEST] <squarecircle> so the best would be to buy a hardware decoder?
[00:25:53 CEST] <DHE> opencl is limited to like 2 filters in ffmpeg, and some limited lookahead in x264
[00:26:13 CEST] <kepstin> squarecircle: all of the "hardware accellerated" decoding in ffmpeg is actually using decoder hardware, yes
[00:26:19 CEST] <DHE> nvenc should be on any gtx card that's less than 4 years old now, except maybe the really low end ones
[00:26:36 CEST] <kepstin> squarecircle: the geforce 8800gt has a dedicated part of the die with a decoder on it (but no encoder)
[00:26:47 CEST] <kepstin> later cards add and encoder too, on some models
[00:26:52 CEST] <squarecircle> kepstin: I don't need any encodet
[00:27:13 CEST] <squarecircle> at the moment, I need only more decoding power
[00:27:14 CEST] <squarecircle> :)
[00:27:17 CEST] <DHE> yeah VDPAU and other APIs exist for video decoding (VDPAU is playback-oriented)
[00:27:31 CEST] <kepstin> huh, the decoder on the 8800gt should work on nouveau via the vdpau api, assuming you have the appropriate firmware
[00:27:45 CEST] <squarecircle> kepstin: hm
[00:27:50 CEST] <squarecircle> thats an idea
[00:28:02 CEST] <squarecircle> I'll try next week
[00:28:13 CEST] <furq> wow, an 8800GT
[00:28:19 CEST] <kepstin> or you can use it with the nvidia driver and the cuda/cuvid api
[00:28:22 CEST] <furq> i think i have one of those in a box somewhere with no heatsink on it
[00:28:30 CEST] <kepstin> either way, it uses the same decoder hardware, just different apis
[00:28:31 CEST] <furq> that'll doubtless come in handy some day
[00:28:49 CEST] <squarecircle> furq: well, thats whats moalding around in the local space here
[00:29:12 CEST] <squarecircle> furq: there are also some Radeon HD6250 and stuff
[00:29:45 CEST] <kepstin> no idea on the speed of the decoder on that card, all they had to support was realtime playback of ~1080p content
[00:29:51 CEST] <squarecircle> hm
[00:29:53 CEST] <squarecircle> ok
[00:34:03 CEST] <kepstin> apparently there was a significant bump to the decoder performance in the geforce 600/700 series (kepler) gpus, which corresponds to when they added an encoder and let people do full hardware transcoding
[00:34:23 CEST] <kepstin> so stuff older than that is probably not worth it unless you're using a contemporary cpu as well
[00:39:31 CEST] <squarecircle> well its junk thats lying around and I don't spend money on it
[00:40:21 CEST] <kepstin> worst case with a modern cpu is that it slows down the decoding :)
[00:41:07 CEST] <squarecircle> Intel(R) Xeon(R) CPU           E5640  @ 2.67GHz
[00:41:21 CEST] <squarecircle> two times on my test bench
[00:42:48 CEST] <squarecircle> so 8C16T
[00:43:20 CEST] <squarecircle> is there a way to enhance the decoding by telling ffmpeg to uses as many cores as possible?
[00:44:31 CEST] <squarecircle> Load average: 111.05 103.14 78.41
[00:44:37 CEST] <squarecircle> at the moment ^^
[00:48:46 CEST] <squarecircle> its obviously not a good idea to start 100 processes in parallel
[00:49:01 CEST] <squarecircle> efficiency goes down
[00:51:18 CEST] <DHE> you can specify -threads 2 (or whatever) before the -i parameter and it applies to the decoder
[00:51:23 CEST] <DHE> but that assumes the decoder supports it
[00:55:58 CEST] <squarecircle> hm
[00:56:35 CEST] <CoreX> you learn something new everyday
[00:57:01 CEST] <squarecircle> DHE: I'll try it
[00:57:25 CEST] <squarecircle> thank you kepstin DHE
[01:12:20 CEST] <LiedFrice> Afternoon :)
[01:13:24 CEST] <LiedFrice> I was curious, can ffplay display a subtitle stream from a pipe like so?
[01:14:39 CEST] <LiedFrice> Everything seems to be encoding right, I just do not see subtitles in the FFplay window: https://pastebin.com/raw/gnCM0GFM
[01:43:09 CEST] <LiedFrice> Any thoughts are much appreciated, could really help with some presentations
[01:51:13 CEST] <LiedFrice> Just an obvervation, vlc player can read the subtitle stream from a pipe and display it, but FFplay does not display anything with the same command
[01:51:17 CEST] <LiedFrice> ffmpeg -f v4l2 -i /dev/video0 -sub_charenc ISO8859-1 -i  MLP1.srt -vcodec huffyuv -scodec text -f matroska - | vlc -
[02:36:00 CEST] <LiedFrice> rip
[02:51:24 CEST] <LiedFrice> Also noted, mplayer can display a subtitle stream in a named pipe while FFplay still isn't displaying any subtitles
[02:51:26 CEST] <LiedFrice> ffmpeg -f v4l2 -i /dev/video0 -sub_charenc ISO8859-1 -i  MLP1.srt -vcodec huffyuv -scodec subrip -f matroska pipe:1 > itsafifo | mplayer itsafifo -vo x11
[03:44:12 CEST] <alexpigment> Hey guys, I saw this patch for FFMPEG to make it large address aware: https://ffmpeg.org/pipermail/ffmpeg-devel/2014-September/163207.html
[03:44:26 CEST] <alexpigment> I'm a little green on patching, but what file specifically is being patched here?
[03:49:13 CEST] <furq> configure
[03:50:25 CEST] <alexpigment> Oh right. Sorry, I'm used to the Windows world where things have file extensions
[03:50:31 CEST] <alexpigment> There's actually a file called configure
[03:50:39 CEST] <alexpigment> Thanks for helping me realize the obvious
[04:55:52 CEST] <dan2wik> I'm having a little trouble with cpu usage on an audio stream.
[04:56:05 CEST] <dan2wik> 1 sec, I'll paste the command line
[04:57:35 CEST] <dan2wik> https://pastebin.com/raw/vuuXs3vM
[04:58:10 CEST] <dan2wik> It is currently using the same amount of cpu as the video encoding I am doing which is rather unacceptable.
[07:30:06 CEST] <zarac> hey folks ; )
[07:34:37 CEST] <durandal_1707> hey
[07:35:36 CEST] <kerio> what's the simplest way of shoving jpeg in a video container with absolute timestamps?
[07:36:18 CEST] <zarac> ; )
[07:36:43 CEST] <zarac> was gonna type a bunch.. about tracker being down and about another bug.
[07:37:01 CEST] <zarac> it solved itself... ; ) (tracker is a bit slow)
[07:39:24 CEST] <zarac> registered and bumped ; )
[08:17:54 CEST] <ussher_> im trying to merge 2 .mp3 files, but the lenght of the output is always determined by the length of the shortest song.  How to make the longest song be the length?  https://pastebin.com/Rw8r6XYB
[08:45:15 CEST] <teratorn> ussher_: run the shorter one through an apad filter filter before amerge?
[08:45:30 CEST] <teratorn> ussher_: perhaps..
[08:46:53 CEST] <ussher_> thanks teratorn, i've rethunk it.  currently looking at looping over the short track to make it longer than the longest track so the shortest track is always the one I want.
[08:47:19 CEST] <ussher_> I'll look into the apad filter next time i get stuck with this current thought line.
[08:47:23 CEST] <ussher_> appreciated.
[08:47:28 CEST] <teratorn> cool good luck
[11:22:22 CEST] <pihpah> How can I extract mov_text subtitles? What are those exactly?
[11:35:35 CEST] <JEEB> they're mov/3gpp/mp4 timed text
[11:35:52 CEST] <JEEB> they're in a container specific format so I'm not sure if they have a standardized format outside of the container
[11:36:11 CEST] <JEEB> you can extract them as srt or ass, for example
[11:44:26 CEST] <pihpah> JEEB: tried with ffmpeg -i {} -map 0:s:0 test.srt did not work out.
[20:23:53 CEST] <flok420> what can be the problem that if avformat_open_input returns -1 (ffmplay and mplayer also fail) on an rtsp stream?
[20:34:07 CEST] <dan3wik> I'm having issues with my audio encoder. I am using 1 ffmpeg instance for video and 1 for audio. The video one sits around 30%, the audio one starts at 15% but ends up around 60% after 2 minutes
[20:34:43 CEST] <dan3wik> Command line for audio is "ffmpeg -f alsa -ar 44100 -ac 1 -i hw:%d -f mpegts -codec:a libtwolame -b:a 32k -muxdelay 0.02 http://%s:%s/%s/1/1"
[21:36:27 CEST] <user_12> How do I convert/copy a WMV to an MP4 (with both auto and video)?  It seems like this is overly complicated, everything I try (i.e., ffmpeg -i in.wmv -c:all copy out.mp4) never work, or the audio or video is missing
[21:36:47 CEST] <user_12> every forum I goto has some other way or other flags to do it
[21:36:56 CEST] <user_12> whats the best way, I dont care about speed/compression
[21:37:08 CEST] <c_14> ffmpeg -i in.wmv out.mp4
[21:37:14 CEST] <c_14> eeh
[21:37:18 CEST] <c_14> ffmpeg -i in.wmv -map 0 out.mp4
[21:38:11 CEST] <user_12> that throws out on-monotonous DTS in output stream 0:0; previous: 685207, current: 678032; changing to 685208. This may result in incorrect timestamps in the output file. which makes the audio choippy
[21:38:54 CEST] <user_12> both of those do
[21:39:05 CEST] <furq> user_12: you can't copy wmv streams into mp4, they don't support any of the same codecs
[21:39:15 CEST] <furq> if you want to reencode it then do what c_14 said
[21:39:25 CEST] <furq> if you have a broken wmv container or something and you want to remux, use mkv
[21:39:57 CEST] <user_12> I did try to re-encode it, it doesn't sound right, its choppy
[21:40:10 CEST] <user_12> mkv?
[21:40:39 CEST] <user_12> How do I go from WVM to Mp4 then>?
[21:40:50 CEST] <user_12> WMV to MP4 rather
[21:40:57 CEST] <furq> you reencode it
[21:41:04 CEST] <user_12> and how do I do that?
[21:41:12 CEST] <furq> you do what c_14 said
[21:41:19 CEST] <user_12> he posted two things, what one
[21:41:23 CEST] <furq> the second one
[21:41:51 CEST] <user_12> and I just said when I 're-encode it' it throws tons of DTS outpit stream errors, which makes the audio choppy
[00:00:00 CEST] --- Sat Aug 26 2017