[Ffmpeg-devel-irc] ffmpeg.log.20160625

burek burek021 at gmail.com
Sun Jun 26 02:05:02 CEST 2016

[01:26:21 CEST] <tommo> can ffmpeg downsample an ac3 file from 384kbps to 192kbps?
[01:27:24 CEST] <BtbN> you mean re-encode at a lower bitrate/quality. downsampling is something diffrent.
[01:27:35 CEST] <tommo> yes btbn
[01:28:04 CEST] <tommo> a show here was broadcast over two channels the first part was in 384kbs the second 192 i want them to match
[01:28:11 CEST] <BtbN> I think ffmpeg has a native ac3 encoder, but I'm not sure. If not, there is definitely support for an external one.
[02:01:47 CEST] <DHE> I believe there is an internal AAC encoder
[02:02:26 CEST] <DHE> a lot of OTA channels offer two audio streams
[02:04:01 CEST] <tommo> well i capped one channel from satellite and the other from cable so i didnt loose anything in the crossover
[02:04:15 CEST] <tommo> but cable always used 384kbps
[02:20:18 CEST] <blue_misfit> yeah the internal AC3 encoder is okay
[02:20:27 CEST] <blue_misfit> E-AC3 not so much
[02:20:43 CEST] <blue_misfit> it works but the native Dolby encoder is much better quality and will set dialnorm metadata correctly etc
[03:15:41 CEST] <snakeryslug> can ffplay play silent black video for X seconds programmatically?
[03:18:21 CEST] <furq> snakeryslug: ffplay -f lavfi -i color=c=black:duration=10
[03:41:14 CEST] <snakeryslug> cool. now i've gotta figure out how to add something to the queue.
[10:29:15 CEST] <_MyStartx_> Hi guys
[10:29:29 CEST] <tommo> morning
[10:30:47 CEST] <_MyStartx_> Is possible than ffmpeg use gpu instead cpu? :)
[10:34:39 CEST] <tommo> yeah
[10:34:40 CEST] <tommo> https://trac.ffmpeg.org/wiki/HWAccelIntro
[10:34:57 CEST] <tommo> you can use use gpu to decode frames and cpu to encode frames
[11:22:36 CEST] <viric> _MyStartx_: you can also use the gpu to encode, but it is not of very good quality
[14:27:16 CEST] <spirou> are there a changelog for ffmpeg somewhere?
[14:27:42 CEST] <JEEB> http://git.videolan.org/?p=ffmpeg.git;a=blob;f=Changelog;h=aabdf9050a75472528bddf515824eb9058e99d40;hb=HEAD
[14:27:56 CEST] <JEEB> that's for features
[14:28:08 CEST] <JEEB> http://git.videolan.org/?p=ffmpeg.git;a=blob;f=doc/APIchanges;h=9ca71b7f8b9d65da53b5b7338e882f00d8792460;hb=HEAD
[14:28:11 CEST] <JEEB> API changes
[14:30:14 CEST] <spirou> thanks
[15:01:24 CEST] <DHE> hmm... I put a feature patch on the mailing list, but it's not listed in that changelog
[15:01:41 CEST] <JEEB> was it merged?
[15:01:54 CEST] <JEEB> basically usually the person doing the patch is supposed to add it to the changelog
[15:07:06 CEST] <DHE> http://git.videolan.org/?p=ffmpeg.git;a=commit;h=e06114fed3afa69187b3dfc09a7a1a25cfd558b3 yes it was
[15:08:55 CEST] <JEEB> yeah, you forgot to add a changelog entry :)
[15:09:05 CEST] <JEEB> I guess you can just send a patch that adds that
[15:11:08 CEST] <DHE> seems there's already been a release or two since then...
[15:12:22 CEST] <JEEB> :D
[15:16:04 CEST] <DHE> well damn...
[15:16:15 CEST] <hero_biz> hi guys
[15:16:26 CEST] <hero_biz> I have a small question
[15:17:09 CEST] <hero_biz> I wonder how I need to configure ffpmeg building process to use x265 multilib feature.
[15:17:18 CEST] <hero_biz> does it use it by default?
[15:17:44 CEST] <JEEB> if it provides a single library to link against then it should work out of the box as long as you link against it
[15:18:09 CEST] <JEEB> if it has to be implemented by the user, then much less likely
[15:18:13 CEST] <DHE> ffmpeg uses x265_api_get() so if that works with multilib then it should be okay
[15:20:05 CEST] <hero_biz> x265 have a multilib.sh that makes 1 lib containing all sub-libs.
[15:20:25 CEST] <hero_biz> just need to change it a little.
[15:20:27 CEST] <JEEB> we don't care
[15:20:33 CEST] <hero_biz> ok,ty info :)
[15:23:01 CEST] <Mooniac> I have corrupted MP4 files as the battery died before writing the moov entry at the end of the file. Can I use ffmpeg, or something else, to repair the broken files?
[15:26:14 CEST] <JEEB> you'd need heuristics based on the files created by the same thing, and there's some more or less shady software (including at least one OSS thing) that tries to do that
[15:26:33 CEST] <JEEB> ffmpeg itself doesn't try to apply any logic like that where you'd input two files (one working and one without the index)
[15:26:33 CEST] <furq> Mooniac: https://github.com/ponchio/untrunc
[15:26:40 CEST] <Mooniac> I have plenty of good sample files.
[15:26:45 CEST] <JEEB> yeah, that's the less shady one
[15:26:50 CEST] <JEEB> although it has lulzy comments in the code
[15:26:51 CEST] <Mooniac> Yes, I've found untruc. But it's for ubuntu. I use Fedora.
[15:27:16 CEST] <Mooniac> I now need to find the package names that correspond to that in Fedora. uh.
[15:28:26 CEST] <JEEB> just build it :P
[15:28:35 CEST] <JEEB> probably doesn't have too many deps if it NIH'd everything
[15:28:58 CEST] <Mooniac> I tried the compilation, it's complaining about packages
[15:30:01 CEST] <furq> https://github.com/ponchio/untrunc/blob/master/Makefile
[15:30:02 CEST] <furq> wtf
[15:30:19 CEST] <furq> https://github.com/ponchio/untrunc/blob/master/Makefile#L13
[15:30:23 CEST] <furq> is this even the right makefile
[15:32:42 CEST] <furq> i guess all of that is qmake boilerplate bullshit but then it's using hardcoded paths to libavformat.a
[15:32:49 CEST] <JEEB> lol
[15:33:15 CEST] <furq> where would we be without all these great build systems to make our lives easier
[15:33:39 CEST] <Mooniac> hmmm ... so any way to make this work on Fedora? Or some alternative?
[15:34:26 CEST] <JEEB> you'll have to poke the build system to be less "this works on my system"
[15:34:32 CEST] <JEEB> or poke the author
[15:34:41 CEST] <JEEB> oh
[15:34:42 CEST] <JEEB> lol
[15:34:49 CEST] <JEEB> their example doesn't even use the damn makefile
[15:35:02 CEST] <JEEB> `g++ -o untrunc file.cpp main.cpp track.cpp atom.cpp mp4.cpp -L/usr/local/lib -lavformat -lavcodec -lavutil`
[15:35:18 CEST] <Mooniac> yes, I tried that line, and that adidn't work
[15:35:22 CEST] <JEEB> yeah... why use build systems if you can just call g++ manually
[15:35:30 CEST] <JEEB> Mooniac: what error(s) did you get?
[15:35:44 CEST] <JEEB> pastebin if much
[15:35:54 CEST] <Mooniac> 5 lines. too much?
[15:36:07 CEST] <JEEB> rather pastebin
[15:36:10 CEST] <JEEB> and link here
[15:36:25 CEST] <Mooniac> https://paste.fedoraproject.org/384583/
[15:36:33 CEST] <JEEB> oh right
[15:36:38 CEST] <JEEB> fedora doesn't package FFmpeg or Libav
[15:36:42 CEST] <Mooniac> but as I said, I don't have these devel packages
[15:36:59 CEST] <Mooniac> right, I don't have libav, and not their devel
[15:37:30 CEST] <JEEB> wonder what FFmpeg/Libav versions their usage expects
[15:37:37 CEST] <JEEB> in general the gist is
[17:32:27 CEST] <utack> Hi. does this blend 4 frames into one, or is the syntax total crap? thanks https://paste.ubuntu.com/17860535/
[17:33:33 CEST] <furq> utack: you can't call -vf or -r twice, it'll just ignore the first ones
[17:33:59 CEST] <utack> any ideas how i could use tblend for something like 4 frames then?
[17:34:01 CEST] <furq> at a guess you want -vf tblend=all_mode=average,tblend=all_mode=average -r 24000/4004
[17:34:15 CEST] <utack> ok thanks, i will try that
[17:35:12 CEST] <utack> but wouldn't that just blend the same two frames, twice?
[17:36:14 CEST] <furq> at a guess it'll actually blend three frames into one
[17:36:24 CEST] <furq> i can't say i've ever used tblend though
[17:36:41 CEST] <utack> i'll give it a try
[19:48:22 CEST] <tombert> hello, I have a dumb question: is there a way to have some kind of output stream and feed that to FFMpeg to transcode
[19:48:55 CEST] <BtbN> ffmpeg can read from stdin, if that's what you're asking?
[19:49:04 CEST] <tombert> yeah
[19:49:11 CEST] <tombert> so I want something like getstream
[19:49:19 CEST] <tombert> getStream "blah" | ffmpeg -i input -c:v libx264 -preset slow -crf 22 -c:a copy output.mkv
[19:49:35 CEST] <tombert> where I want input to be stdin
[19:49:49 CEST] <furq> ffmpeg -i pipe:0
[19:49:57 CEST] <DHE> or just "ffmpeg -i -"
[19:49:57 CEST] <BtbN> Or - , or /dev/stdin
[19:50:17 CEST] <tombert> I didn't know that stdin was a file...lol.
[19:50:58 CEST] <DHE> under unix, lots of things are files. your terminal, TCP and UDP sockets, epoll devices, directories..
[19:51:16 CEST] <tombert> I knew about all of those, I should have assumed stdin as well
[19:52:05 CEST] <DHE> when you run an application with 'appname < somefile' all it does is replace stdin with the open file instead of the regular terminal
[20:45:50 CEST] <hero_biz> guys,a question
[20:46:06 CEST] <hero_biz> i'm trying to build ffmpeg with tessarect support.
[20:46:26 CEST] <hero_biz> i have installed it from repository, but I get this error:
[20:46:29 CEST] <hero_biz> "ERROR: tesseract not found using pkg-config"
[20:46:33 CEST] <hero_biz> any idea why?
[21:18:43 CEST] <DHE> and he's gone
[22:01:17 CEST] <Bray90820_> Prob a dumb question but is ffmpeg installed by default on ubuntu
[22:29:52 CEST] <kepstin> Bray90820: depending on the ubuntu version, some libraries from ffmpeg or libav may be installed by default, but the command line tool won't be.
[22:30:11 CEST] <Bray90820> Yea I figured that out
[22:47:41 CEST] <Bray90820> What do these errors mean?
[22:47:41 CEST] <Bray90820> http://pastebin.com/raw/uBzaC8VH
[00:00:00 CEST] --- Sun Jun 26 2016

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