[Ffmpeg-devel-irc] ffmpeg.log.20170924

burek burek021 at gmail.com
Mon Sep 25 03:05:01 EEST 2017

[00:21:53 CEST] <brash> Anyone familiar with using ffmpeg api to copy a video stream from one container to another?
[00:56:17 CEST] <c3r1c3-Win> brash: hoorible recommendation by me but... if you look at the code in OBS it uses FFMPEG to remux stuff.
[00:57:47 CEST] <thebombzen> alternatively, look at the code in ffmpeg.c
[00:57:55 CEST] <thebombzen> what it does when you pick -codec copy
[01:21:27 CEST] <brash> Those sound like good recommendations. Thanks c3r1c3-Win and thebombzen.
[03:12:46 CEST] <kevinn_> Hi, I am using libav to decode frames encoded with x264 and I am wondering how to decrease latency (or what appears to be latency) between the source and destination. I am *fairly* confident that the frames are encoded in such a way that there shouldn't be any latency in the frames (with zerolatency and i_keyint_max=1). Any help would be greatly appreciated!
[03:44:43 CEST] <DHE> zero latency means that the old API (avcodec_encode_video2) will return the encoded version of the exact frame put in, and the new API should allow you to alternate between send_frame and receive_packet to the same effect
[03:48:35 CEST] <kevinn_> DHE: I am actually using x264 to encode, and yes that is what I have been led to believe is happening. I think there might be something wrong with the way I am decoding (through libav)
[03:48:46 CEST] <kevinn_> is there anything special I need to do on the decode end?
[03:56:33 CEST] <DHE> I doubt it. zerolatency source material does speed up decoding in the same way as well
[04:17:52 CEST] <furq> https://web.archive.org/web/20150507012544/http://x264dev.multimedia.cx/archives/249
[04:17:55 CEST] <furq> kevinn_: see comment #8
[04:33:30 CEST] <royyuuki> Hi
[04:34:00 CEST] <royyuuki> I was advised by your rep in Twitter that I should use IRC to contact you guys for complex discussions.
[04:35:23 CEST] <royyuuki> Can someone please send me a PM on how can I read an error log from FFmpeg? I use -xerror to QC all of my video files that I work with, however, the error log only shows the memory address and I dont know how to convert that to a specific TC/frame so I can manually check the problem
[09:10:45 CEST] <stunts513> im a bit lost. i just transcoded a live stream to an mp4 and apparently there were some hiccups along the way as i have a 2.3gb mp4 thats a little over 3 min long.
[09:11:11 CEST] <stunts513> it keeps trying to seek past that but has issues. any ideas?
[10:19:17 CEST] <horox> Hello, I have been using older versions of ffmpeg, where you could click in the video file while it is played and scrub it forward and backward with the mouse, as well as if you clicked at the left edge of the video window, it would be played from the beginning, if you clicked in  the middle, it would play from the middle and so on. On recent builds this feature does not work any more, is there a way to reactivate it at compile-time,
[10:19:18 CEST] <horox> or is there a flag for it?
[10:43:41 CEST] <drv> horox: seeking in ffplay is right mouse button now
[11:04:13 CEST] <horox> right. Thanks!
[11:05:06 CEST] <horox> I have mouse gestures on right mouse button, so I did not recognize that.
[11:09:16 CEST] <horox> I have another question regarding video files played with wrong color tint. FFMPEG has support for Magic Lantern .mlv files for quite a while now, but they are all played back with a greenish color tint - I guess its better to ask that in the ffmpeg-devel channel?
[12:00:24 CEST] <royyuuki> 10:35 royyuuki: Can someone please send me a PM on how can I read an error log from FFmpeg? I use -xerror to QC all of my video files that I work with, however, the error log only shows the memory address and I dont know how to convert that to a specific TC/frame so I can manually check the problem
[15:25:40 CEST] <nominator> hi, is there any way how to convert MPD files to any other format using ffmpeg?
[15:34:51 CEST] <arpu> any one an idea why i get EOF timestamp not reliable always after 31:28:26.06
[15:35:00 CEST] <arpu> http://lpaste.net/742000276633812992
[15:36:08 CEST] <arpu> http://lpaste.net/8267065609548726272 ffmpeg command testsrc
[19:35:32 CEST] <faLUCE> Hello. Is it true that for an audio+video mpegts stream, audio and video are already synchronized at the source (---> no need to sync them on the demuxer) because the mpegts muxer uses a common PCR for both the tracks ?
[22:02:50 CEST] <azarus> I sometimes record my desktop and I'd like to know what formats are usable. It's an old laptop (Core 2 Duo P8600 to be precise) so not dropping frames is kinda difficult.
[22:03:21 CEST] <azarus> I used h264 in the past, is there any viable alternative?
[22:03:35 CEST] <azarus> I tried vp8, but it's *way* too slow to encode.
[22:10:50 CEST] <Mavrik> azarus, it's usually way better to record into a very fast inefficient format
[22:10:53 CEST] <Mavrik> and then reencode
[22:11:13 CEST] <azarus> Mavrik: Sure, makes sense. What are some very fast, inefficient formats?
[22:11:16 CEST] <Mavrik> Something like losless FFV1, or ultrafast losless H.264 profile
[22:11:24 CEST] <Mavrik> *libx264
[22:11:32 CEST] <Mavrik> Yeah, the video will be hugeish (a few 10GB)
[22:11:44 CEST] <Mavrik> But then you can encode it at your leisure without worrying about dropped frames
[22:12:24 CEST] <azarus> Great, thanks!
[22:12:44 CEST] <Mavrik> On ffmpeg wiki there's info on how to do losless H.264 :)
[22:12:48 CEST] <Mavrik> FFV1 too probably
[22:17:01 CEST] <azarus> Huh, with libx264 I get 26 fps, with FFV1 I get 16.
[22:17:31 CEST] <Mavrik> possibly. Did you actually use a fast preset with libx264?
[22:19:34 CEST] <azarus> ultrafast.
[22:20:48 CEST] <Mavrik> try with huffyuv as well, that was the fastest one. Bad compression tho :)
[22:32:53 CEST] <furq> ffvhuff is even faster and should compress better
[22:33:07 CEST] <furq> if you don't mind it only being supported by ffmpeg
[22:33:42 CEST] <furq> utvideo is also a decent choice if you mostly care about speed
[22:33:49 CEST] <furq> ffv1 and x264 lossless will compress much better than either
[22:55:10 CEST] <Snaggle> is enable-vda supposed to work on OS X? When I try it, config.log says that its dependencies vda_framework pthreads arent satisfied, but I couldnt find any errors in config.log relating to those two deps.
[23:03:00 CEST] <Snaggle> to expand: with ffmpeg-3.3.4, I get audiotoolbox, vda, videotoolbox_hwaccel, and xvmc providing hardware acceleration. But with git HEAD, I need to not-enable-vda for ./configure to finish and then I get no hardware acceleration.
[23:10:41 CEST] <Mavrik> Snaggle, afaik VDA is obsolete and nonexistent in new macOS
[23:14:40 CEST] <Snaggle> Mavrik: ok, but since Im not on latest-macOS (still on 10.11), and the configure option to disable it still exists, it stands to reason that it _should_ still build on my system, right?
[23:14:53 CEST] <Mavrik> Uhh.
[23:15:08 CEST] <Mavrik> It's pretty unmaintained tbh.
[23:15:13 CEST] <Mavrik> So I guess try with older ffmpeg?
[23:18:45 CEST] <Mavrik> Snaggle, you should have videotoolbox available though, is there an issue with that?
[23:18:56 CEST] <Snaggle> 3.3.4 configure output shows a whole lot of hwaccels (*_videotoolbox, *_vda, and *_xvmc), but HEAD has lost all of those. Im trying to understand why, or if ffmpeg is still using hwaccel, but just not listing it in the configure output.
[23:20:37 CEST] <Snaggle> ugh. I have disable-autodetect in ./configure.  too many options to parse them all by eye
[23:21:35 CEST] <Snaggle> ok.  videotoolbox comes back by fixing that
[23:23:06 CEST] <Snaggle> !lart trying to go for deterministic builds and then forgetting how I got there
[00:00:00 CEST] --- Mon Sep 25 2017

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