[Ffmpeg-devel-irc] ffmpeg.log.20190812

[burek]

[00:41:32 CEST] <ncouloute> I'm trying to concat multiple mp4 files together. It seems I get a +-8 frame offset between clips.. How can I maintain the video frame location after concatenation.Using ffmpeg cmd line
[01:56:42 CEST] <Compressionz> Do we have a way to set the audio output device for FFplay? Or is it always the default device?
[01:57:11 CEST] <cehoyos> "We" not but SDL has an option (just a moment):
[01:58:16 CEST] <cehoyos> I have:
[01:58:24 CEST] <cehoyos> export SDL_AUDIODRIVER=alsa
[01:58:32 CEST] <cehoyos> export AUDIODEV=plughw:0,1
[01:58:49 CEST] <cehoyos> in my .bashrc to select alsa 0.1 as default device for ffplay
[01:59:10 CEST] <cehoyos> (actually for sdl)
[02:00:22 CEST] <Compressionz> Thats great! Thats a workaround at least :D  Thanks a bunch for that info...Is it possible on Windows, too?
[02:04:09 CEST] <Compressionz> I'd love to be able to route audio from FFplay into a virtual sound device on Windows but i've had to use this alternative https://github.com/audiorouterdev/audio-router
[02:11:48 CEST] <DHE> well ffplay isn't really intended as a fully featured video player. more as a proof of concept, and it's convenient to run filter tests with it and stuff
[02:11:49 CEST] <DHE> oh goddammit
[04:10:58 CEST] <JAK-Zero> hey, just wanted to ask a quick question. On Windows, is there a way to update ffmpeg, or do I just have to download new versions myself?
[04:12:11 CEST] <TheAMM> No*, yes
[04:12:24 CEST] <TheAMM> (* technically depends on how you installed ffmpeg)
[04:13:18 CEST] <JAK-Zero> oh? How can you install ffmpeg on Windows, besides downloading it from here? https://ffmpeg.zeranoe.com/builds/
[05:25:12 CEST] <KombuchaKip> What is the simplest way of determining the length of the data field in an AVFrame?
[05:37:53 CEST] <Compressionz> heyo, so earlier I was asking about if it were possible to change the output audio device for ffplay. Cehoyos pointed out you can set some SDL enviromnent variables to change the device https://i.imgur.com/tzVblpm.png
[05:38:02 CEST] <Compressionz> Thats great news but I'd also like to do the same on Windows. I've tried both the SDL_PATH_DSP and AUDIODEV variables but nothing seems to change... However if I make the SDL_AUDIODRIVER variable an incorrect one I do get this error https://i.imgur.com/aVy3xUe.png am I doing something wrong or does FFplay/SDL not support this on Windows..? Also her
[05:38:03 CEST] <Compressionz> es what I used to set directsound as the driver https://wiki.libsdl.org/FAQUsingSDL#Win32-1
[06:00:38 CEST] <Abbott> whatsapp lists the video requirements as "less than 16MB" and recommended is h.264, aac, and mp4 container. so if I ffmpeg -i test.mkv -c:v libx264 -c:a aac output.mp4, why would the video not play in whatsapp
[06:07:00 CEST] <Compressionz> The only alternative I can come up with is setting the default device to Virtual Audio cable, starting ffplay, and changing device back to speakers.
[06:19:44 CEST] <Compressionz> I scripted a workaround in AutoHotkey if anyone is interested https://pastebin.com/XXgHNMUh
[06:59:43 CEST] <Compressionz> Keep getting disconnected :b  But yea hopefully someone finds that workaround useful until another method comes around
[09:16:19 CEST] <MoziM> what's the best way to 'compress' duplicate frames without altering the length of the video itself?
[09:17:58 CEST] <MoziM> let's say i have 10 seconds of footage where nothing changes on the screen, can a codec tell a video player to simply repeat the same image at n FPS for 10 seconds? therefore resulting in a really small file?
[09:34:51 CEST] <pink_mist> MoziM: that's what most modern codecs likely will do, yes ... it might not be 100% like that, but it should be fairly close
[09:38:52 CEST] <MoziM> which codec do you recommend?
[09:39:15 CEST] <pink_mist> x264 probably
[09:41:06 CEST] <MoziM> that's it?
[09:41:17 CEST] <MoziM> :o
[11:42:43 CEST] <rahulch> Hi, I have a webcam that is being used for a videocall. During the call, is it possible to capture the frames that I can see in my videocall application?
[14:37:44 CEST] <goel> Hi I am copying the packets from one mp4 to a new mp4 file using FFmpeg/libav. I noticed when looking at the difference in both input and output files that the difference is only within the trailer. The metadata (when using ffprobe) of the output mp4 file in comparison to the input mp4 is only different in two places. The encoder version i.e. Lavf5
[14:37:45 CEST] <goel> 7.56.100 vs Lavf58.30.100 and the tbn for the input was 16384 compared to the output which stated 90K. Is it possible to change the metadata of the output file (AVFormatContext) before calling av_write_trailer() ?
[14:41:41 CEST] <DHE> you're supposed to do it before writing av_write_header actually. also I don't see a way of controlling that beyond using AVFMT_FLAG_BITEXACT which really just strips out the version number for consistency
[14:47:38 CEST] <goel> I am new to FFmpeg and libav, is there a specific method which allows me to modify the metadata?
[14:47:48 CEST] <goel> And thanks for the help DHE
[14:48:11 CEST] <DHE> I'm looking at the source. doesn't look like it's editable beyond bitexact mode
[14:48:33 CEST] <goel> I just wanted to have both files being byte for byte the same.
[14:48:33 CEST] <DHE> which like I said, mostly either strips out the metadata or makes it version-agnostic with simply "Lavf"
[14:48:42 CEST] <DHE> well you definitely want bitexact mode then
[14:49:38 CEST] <goel> Ok thanks, I'll have a look at bitexact mode. I appreciate your help!
[14:57:36 CEST] <goel> It removed encoder information from the output file. I mean we wanted to make all the metadata in the trailer byte for byte the same as the original but I am not sure if that is possible.
[14:58:30 CEST] <durandal_1707> are you creating fake video by any chance?
[14:59:04 CEST] <goel> I am not sure what you mean by fake video?
[14:59:24 CEST] <goel> This is a beginning process of prototyping a program.
[14:59:37 CEST] <goel> We wanted to just deconstruct some videos and rebuild them.
[15:00:06 CEST] <goel> Hence, the fact that the output was different from the input was interesting.
[17:34:06 CEST] <pk08> hi
[17:35:07 CEST] <pk08> i can make 2 volumebars (mono and stereo) using showvolume filter but i am getting only 2 bars even if input audio have more channels
[17:35:38 CEST] <pk08> can any one tell me, is this limitation of showvolume filter or am i missing something?
[17:41:49 CEST] <durandal_1707> full command missing
[17:43:04 CEST] <durandal_1707> there is no limitation on number of channels
[17:44:59 CEST] <fred1807> can I restream/forward a live stream from twtich to youtube?
[17:45:50 CEST] <pk08> https://pastebin.com/60FSjetC
[17:46:15 CEST] <pk08> durandal_1707: above command
[17:47:37 CEST] <durandal_1707> try swapping w and h values
[17:49:51 CEST] <durandal_1707> or perhaps your athers channels are croped out by that overlay command
[17:50:13 CEST] <durandal_1707> so use x=0
[17:51:11 CEST] <pk08> ok, let me try
[17:53:19 CEST] <durandal_1707> you can use q to stop encoding
[18:02:38 CEST] <pk08> durandal_1707: i have set x=0 and tried but still it outputs only 2 audiobars
[18:03:05 CEST] <pk08> i have read somewhere that, we can only outputs 2 volumebars
[18:03:10 CEST] <pk08> but i cant find now
[18:03:48 CEST] <durandal_1707> lies
[18:04:17 CEST] <durandal_1707> your audio have 2 channels only
[18:04:51 CEST] <durandal_1707> if you use only showvolume filter you will see
[18:09:06 CEST] <pk08> check this: https://pastebin.com/1UTJWZJc
[18:09:51 CEST] <pk08> you can check my command and see output of input stream and mapping of streams
[18:11:23 CEST] <durandal_1707> i doubt you can select audio stream like that
[18:11:59 CEST] <durandal_1707> 0x34 is specific stuff that does not work with filters
[18:13:10 CEST] <pk08> but you can see its working
[18:13:27 CEST] <pk08> if you see in ffmpeg mapping
[18:13:54 CEST] <pk08> you will find stream: 0:1 is being used as input
[18:16:40 CEST] <durandal_1707> your encoding format is stereo
[18:17:20 CEST] <durandal_1707> and there is implicit conversion in log
[18:17:38 CEST] <durandal_1707> why you use mp2?
[18:18:40 CEST] <durandal_1707> you will need to use aformat before showvolume filter if you need mp2
[18:20:04 CEST] <durandal_1707> otherwise use better codec
[18:20:07 CEST] <pk08> im testing audio output so leave mp2 for now
[18:20:33 CEST] <pk08> and i am using -f mpeg and outputing as file pipe
[18:20:48 CEST] <pk08> and using that piped output to play on screen
[18:20:59 CEST] <pk08> so there is nothing to do with mp2 and -f mpeg
[18:21:35 CEST] <durandal_1707> no
[18:21:51 CEST] <durandal_1707> its stored as stereo
[18:22:05 CEST] <durandal_1707> so use aac or copy ac3
[18:59:15 CEST] <pk08> thanks durandal_1707, its working now!
[22:34:12 CEST] <Thomas_J> I have been spending all day trying to compile a version of gnutls in an aarch64 OS with unending dependency and compile errors. My latest issue is now a massive "libgnutls.so: undefined reference" error compiling for the target psktool. I am now just remembering back last month on this channel that I was told that gnutls is now part of the ffmpeg core. Am I remembering this correctly? If so, can I compile the latest ffmpeg without the --enable-gnutls
[22:34:12 CEST] <Thomas_J> and still expect a rtmps push to Facebook to work?
[23:10:29 CEST] <cehoyos> Thomas_J: gnutls is definitely not part of FFmpeg, gnutls is an optional dependency of FFmpeg
[23:18:04 CEST] <Thomas_J> Dang! Well, back to getting gnutls compiled. Forr just streaming out with rtmps as a client, do I really need the psktool?
[23:18:12 CEST] <BtbN> Why not just openssl?
[23:18:58 CEST] <Thomas_J> I don't think that Facebook handshaked with SSL.
[23:20:48 CEST] <cehoyos> openssl and gnutls should be two different external libraries that offer the same functionality for FFmpeg
[23:21:16 CEST] <cehoyos> (That may not be true in every detail but there is a good chance it works)
[23:21:29 CEST] <Thomas_J> I guess that it wouldn't hurt to give it a try.
[23:21:50 CEST] <BtbN> Also, why build it yourself? Does your distro not package any ssl lib ffmpeg supports?
[23:26:14 CEST] <Thomas_J> Accordig to JEEB there has been a problem that has appeared in rtmps encrypting with gnutls that makes handshaking with Facebook fail. He says that he fixed it but it hasn't trickled down into all the repositories. The version that is in the debian repos still has the problem. I tried to use it and it fails still.
[23:27:18 CEST] <BtbN> so... don't use gnutls then?
[23:27:36 CEST] <Thomas_J> Besides, this version is so bloated with all possible uses, it's humongas.
[23:29:26 CEST] <Thomas_J> I need to use what works with facebook. I got it running like a champ last month ago but I have a new ARM64 unit I need to run it in running Armbian.
[23:30:28 CEST] <BtbN> And they don't package openssl there?
[23:30:45 CEST] <Thomas_J> And this is where I am trying to remember my conversations with JEEB on this channel.
[23:31:51 CEST] <Thomas_J> I'm trying to duplicate what I did last month running it in a Raspberry PI 3B with Raspbian.
[23:35:11 CEST] <cehoyos> Did you see https://lists.ffmpeg.org/pipermail/ffmpeg-devel-irc/2019-July/date.html ? It's currently broken though...
[23:37:00 CEST] <BtbN> I really don't see the big issue
[23:37:09 CEST] <BtbN> if they have a known issue with gnutls... use something else
[23:45:17 CEST] <Thomas_J> As I say, The problem with rtmps has been fixed and I do have a running version using rtmps the core support in another ARM unit but I am trying to duplicate that. Actually, it is slowly coming back to me. I don't think that I used gnutls at all. I think I used the internal core support for the rtmps after it has been fixed.
[23:46:25 CEST] <BtbN> ...?
[23:46:29 CEST] <BtbN> "the internal core support"?
[23:46:38 CEST] <BtbN> ffmpeg did not NIH a ssl lib as of yet
[23:48:13 CEST] <Thomas_J> Yes. ffmpeg, in it's docs shows the command for rtmps use and a separate one for using the gnutls module to handle encryption
[23:49:32 CEST] <furq> the internal rtmps stuff still depends on a linked tls lib
[23:51:31 CEST] <furq> also you should just be able to link with your distro provided gnutls
[23:53:18 CEST] <BtbN> furq, aparently it's older and has a bug that breaks it talking to Facebook
[00:00:00 CEST] --- Tue Aug 13 2019