[Ffmpeg-devel-irc] ffmpeg.log.20160604

burek burek021 at gmail.com
Sun Jun 5 02:05:02 CEST 2016

[02:22:45 CEST] <votz> In attempt to cross compile ffmpeg  v2.8.6 for armeabi-v7a, I encounter lib.m errors, both with Android's libm.h and libavutil/libm.h. Error log: http://pastie.org/private/smdyrzu1mvun8vwtzr5ucg. From Googling, similar math.h related compilation errors have occurred when cross compiling for windows, MIPS, ARM, etc. Any idea how to resolve these errors?
[04:31:41 CEST] <nicolas17> I need to make a video with a thousand image files, the filenames are sorted but do *not* have consecutive numbers, so I can't use something like image%03d.jpg
[04:31:53 CEST] <c_14> -pattern_type glob
[04:31:56 CEST] <nicolas17> does ffmpeg support that, or should I make a bunch of consecutively-numbered symlinks?
[04:32:02 CEST] <nicolas17> c_14: oh good
[04:37:38 CEST] <nicolas17> c_14: any chance I can put the filename into the video as text? I can't see any relevant expanded variable in the drawtext filter
[04:38:29 CEST] <c_14> not really, no
[04:38:37 CEST] <c_14> the image2 demuxer doesn't export that information
[04:56:05 CEST] <nicolas17> bah, I get some images upside down
[04:56:18 CEST] <nicolas17> I guess they are upside down and relying on EXIF orientation tags to display properly in normal photo viewers
[17:41:23 CEST] <Pistos> This is proving hard to websearch: I just want to take the literal black (#000000) and convert it to alpha in a video file.  Being able to set some variance/threshold would be nice, though.
[17:42:16 CEST] <Mavrik> It's called colorkeying
[17:42:17 CEST] <Mavrik> https://ffmpeg.org/ffmpeg-filters.html#colorkey
[17:42:22 CEST] <Mavrik> Colorkey filter will do it for you :)
[17:42:45 CEST] <nicolas17> if you have any lossy encoding in your input images, you will need a threshold
[17:42:50 CEST] <Pistos> Thank you, I'll read up on it, Mavrik!
[17:44:05 CEST] <Lantizia> Hey I'd like to backup my dvd's to my hdd... at first I tried handbrake but it just seems too over the top for the job so I'm thinking command line might be better
[17:44:36 CEST] <Mavrik> For DVDs not so much :/
[17:45:02 CEST] <Lantizia> so I'm wondering two things a) can ffmpeg be told it's "source" file is a dvd title number? (rather than working out which VOB's put together are the same title) and b) can it encode to webm these days?
[17:45:16 CEST] <nicolas17> Lantizia: is it a commercial movie?
[17:46:07 CEST] <Lantizia> some tv, some movies - some are region 1, some 2, some no region at all - i'm aware of the process for copying the VOB's off successfully in any of those cases
[17:46:20 CEST] <nicolas17> so you already decrypted them?
[17:46:40 CEST] <Lantizia> i just changed the region on the drive and copies the VOB's to disk using the file manager basically
[17:46:44 CEST] <Lantizia> *copied
[17:47:08 CEST] <nicolas17> afaik they will still be CSS-encrypted, and ffmpeg won't decrypt them for you
[17:47:30 CEST] <furq> Lantizia: http://dvdbackup.sourceforge.net/
[17:47:36 CEST] <Lantizia> afaik handbrake just uses ffmpeg under the hood anyway
[17:47:47 CEST] <ATField> Lantizia: Re: question b: ffmpeg can encode to both vp8 and vp9.
[17:48:04 CEST] <furq> you can use that to decrypt and to extract individual titles
[17:48:37 CEST] <furq> i haven't figured out a good way of getting chapter markers with it yet but i normally don't really care
[17:50:57 CEST] <Pistos> Mavrik: I'm having troulbe finding the right syntax to specify both the colour and the similarity option.  :\  Could you provide an example?
[17:51:22 CEST] <Mavrik> uhh
[17:51:37 CEST] <Mavrik> -vf colorkey=color=something:similarity=0.8 ?
[17:51:47 CEST] <Mavrik> Check the wiki / docs for how to do vf :/
[17:51:55 CEST] <Pistos> Mavrik: Yeah, I tried that...
[17:52:53 CEST] <furq> -vf colorkey=0x000000:0.5
[17:53:19 CEST] <furq> if you want a hex color
[17:53:24 CEST] <furq> you can just use "black" though
[17:53:37 CEST] <Mavrik> Pistos, did you check if your ffmpeg is even new enough?
[17:53:43 CEST] <Pistos> I've tried that, too, with "black"... hmm...
[17:53:51 CEST] <Pistos> Well, it isn't complaining about the syntax?  :D
[17:53:59 CEST] <Pistos> 2.8.6 it says.
[17:54:11 CEST] <furq> i take it there's no error and it just doesn't work
[17:54:14 CEST] <Pistos> Mhm
[17:54:23 CEST] <furq> try a higher similarity/blend i guess
[17:54:24 CEST] <Pistos> Well, it could be that kdenlive isn't handling it right,
[17:54:34 CEST] <Pistos> even though I've used many videos with alpha in kdenlive before.
[17:54:41 CEST] <Pistos> Yeah, I'll put it at .99 see what happens.
[17:54:59 CEST] <furq> oh right if you're converting it to alpha then it depends on the codecs and the player
[17:55:26 CEST] <Mavrik> Yeah, encoding it to yuv420 won't keep the alpha :)
[17:55:26 CEST] <nicolas17> what is your output format? does it even support alpha?
[17:55:35 CEST] <Pistos>     Stream #0:0(und): Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv444p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 29.97 fps, 30k tbn, 29.97 tbc (default)
[17:55:45 CEST] <furq> you probably want -pix_fmt yuva420p or similar
[17:55:47 CEST] <Lantizia> furq, well I think I've got the hang of dvdbackup now - thanks for letting me know... think I can pipe this to ffmpeg?
[17:55:47 CEST] <Pistos> I can turn this intou any output format at all, whatever will work.
[17:55:53 CEST] <Pistos> furq: Okay, will try.
[17:56:30 CEST] <Mavrik> Does H.264 support alpha in ANY of configurations?
[17:56:32 CEST] <Lantizia> tbh the only thing handbrake was doing which was annoying me was (I *think*) autocropping stuff
[17:56:33 CEST] <furq> Lantizia: i can't say i've used it much
[17:56:45 CEST] <Lantizia> in VLC I'd see that 'Display Resolution' sometimes didn't match 'Resolution'
[17:56:46 CEST] <furq> Mavrik: i'm pretty sure h.264 supports alpha but i've never seen a player that supported it
[17:56:54 CEST] <furq> not that i've looked very hard
[17:57:01 CEST] <hispeed67> woohoo... ordered a new (for me) workstation...
[17:57:13 CEST] <hispeed67> sorry wrong channel
[17:57:16 CEST] <Pistos> furq: Still not working... anyway, I'm running out of time, re: deadline, so I'll just give up.
[17:57:17 CEST] <Mavrik> Finding a player that supports anything over yuv420 is rare :/
[17:57:18 CEST] <Lantizia> I'm just after something that doesn't alter the content of the audio/video at all - just encodes them
[17:57:22 CEST] <Pistos> It isn't that important, but would have been nice to have.
[17:57:26 CEST] <Mavrik> hispeed67, we can still say yay! ;)
[17:57:58 CEST] <Lantizia> come to think of it I remember doing this before - used to use this program that did it from DVD to Theora ... might look at that again
[17:57:58 CEST] <Pistos> Last thing I tried was: -vf "colorkey=0x000000:0.99" -pix_fmt yuva420p
[17:58:01 CEST] <hispeed67> what's a good channel for hardware discussion? i need to get a video card for it.
[17:58:26 CEST] <furq> Lantizia: you could just use the handbrake cli
[17:58:39 CEST] <Lantizia> furq, handbrake won't do webm though
[17:58:45 CEST] <furq> oh right
[17:59:19 CEST] <hispeed67> furq: if i use ffmpeg for my video editing, will a good video card (vs. onboard video) make a difference??? (i.e. the video isn't playing during editing)
[17:59:26 CEST] <furq> not really
[17:59:42 CEST] <nicolas17> hispeed67: I don't think ffmpeg has GPU acceleration for encoding etc
[17:59:46 CEST] <furq> it might be helpful for decoding but it'll be basically worthless for encoding
[17:59:55 CEST] <furq> except maybe for a few filters
[19:50:33 CEST] <wallbroken> hi
[19:50:40 CEST] <wallbroken> is there some way to sync audio and video?
[20:16:35 CEST] <CoJaBo> wallbroken: Is it out of sync by a constant amount, or variable?
[20:23:55 CEST] <wallbroken> CoJaBo
[20:24:07 CEST] <wallbroken> at the start the delay is x
[20:24:13 CEST] <wallbroken> then inchreases
[20:28:44 CEST] <CoJaBo> wallbroken: linearly? or don't youn know..
[20:29:34 CEST] <wallbroken> i think linearly
[20:29:46 CEST] <wallbroken> i can make a diff between video track
[20:29:49 CEST] <wallbroken> and audio track
[20:29:55 CEST] <wallbroken> i have them separated
[20:29:59 CEST] <wallbroken> and i'm trying to mux
[20:30:29 CEST] <CoJaBo> Something like that is usually because framerate was rounded while saving; tweak the fps or the audio speed till they're the same length, then shift it to line up
[20:31:11 CEST] <CoJaBo> ..or is it a file you're creating, not one you're trying to fix?
[20:33:50 CEST] <newuser145> Hello. I got two wav files which i need to merge. one's volume is too low, other's too high. Can something be done to balance the volume? Thanks in advance !
[20:34:28 CEST] <wallbroken> CoJaBo, video is a little faster than video
[20:34:47 CEST] <wallbroken> *audio is a little faster than video
[21:12:41 CEST] <ATField> Whats a proper way of converting one codecs bitrate into another ones, for quality preservation? Say theres a 60-second long vp8-encoded video at a bitrate of 1000kb\s, if you convert that into vp9, the bitrate doesnt have to be the same 1000kb\s, since vp9 is more efficient than vp8, right?
[21:12:52 CEST] <furq> there is no proper way
[21:13:30 CEST] <Demon_Fox> If you're recompressing the video, you're going to lose quality
[21:13:49 CEST] <furq> you shouldn't be using bitrate anyway unless you need a fixed filesize or you're livestreaming
[21:13:53 CEST] <furq> use crf
[21:14:13 CEST] <Demon_Fox> You can also use crf with a bitrate cap
[21:14:20 CEST] <Demon_Fox> Even for live streaming
[21:14:25 CEST] <furq> with vp9, sure
[21:15:35 CEST] <Demon_Fox> If you don't have to recompress that video, don't
[21:16:08 CEST] <ATField> Demon_Fox: Well, yes. But there could be various degrees of quality loss, so I was wondering how both output quality and filesize could be optimized.  furq: Unfortunately the goal is to get into a filesize limit, so crfs not the best option.
[21:16:38 CEST] <Demon_Fox> I'm going to go with furq on this one
[21:16:57 CEST] <furq> if you have a filesize limit then you already know what target bitrate to use
[21:17:03 CEST] <Demon_Fox> If you're not constrained, experiment with crf
[21:17:06 CEST] <ATField> Ill try reading on crf+bitrate limit. Thanks for the hint.
[21:17:11 CEST] <Demon_Fox> Find a setting that still looks good
[21:17:18 CEST] <furq> there's not really much you can do to optimise that other than using a slower preset
[21:17:22 CEST] <furq> or whatever libvpx calls that
[21:17:24 CEST] <furq> is it -speed
[21:17:32 CEST] <Demon_Fox> and cap it if live streaming is an issue
[21:17:59 CEST] <furq> i wouldn't use crf + bitrate if you're constrained by filesize
[21:18:02 CEST] <Demon_Fox> or you have some other physical demand
[21:18:03 CEST] <furq> just do a 2-pass bitrate encode
[21:18:14 CEST] <Demon_Fox> It sounds like he's doing live streaming
[21:18:25 CEST] <Demon_Fox> I absolutely hate 2 pass encoding
[21:18:30 CEST] <furq> he said "get into a filesize limit"
[21:18:31 CEST] <Demon_Fox> It's terribly slow
[21:18:48 CEST] <Demon_Fox> ok
[21:18:59 CEST] <furq> and yeah it is but if you want best quality at target size it's the only real option
[21:19:19 CEST] <furq> i imagine it's amazingly slow with libvpx-vp9 though
[21:19:19 CEST] <Demon_Fox> Yeah...
[21:19:31 CEST] <furq> it's slow enough doing one pass
[21:19:49 CEST] <Demon_Fox> You should take a look at AV1 if you think vp9 is slow :P
[21:19:58 CEST] <furq> is that the aomedia codec
[21:20:12 CEST] <Demon_Fox> It's supposed to be half the bitrate of h.265 at the same quality
[21:20:16 CEST] <furq> ha
[21:20:17 CEST] <furq> sure
[21:20:20 CEST] <Demon_Fox> where vp9 was only supposed to compete with h.265
[21:20:31 CEST] <furq> you mean like how h.265 is supposed to be half the bitrate of h.264 at the same quality
[21:20:43 CEST] <Demon_Fox> h.265 wasn't supposed to be half
[21:20:54 CEST] <Demon_Fox> more like 70% of the bitrate at the same quality
[21:21:06 CEST] <furq> i've read that figure a bunch of times, i assumed it came from somewhere official
[21:21:18 CEST] <Demon_Fox> and av1 takes from Daala, Thor, vp9 and vp10
[21:21:42 CEST] <ATField> Is there a tech-table somewhere that lists this supposed bitrate ratios between codecs, maybe (e.g. you mean like how h.265 is supposed to be half the bitrate of h.264 at the same quality)?
[21:21:51 CEST] <furq> i would hope they'd optimise for usability over compression
[21:21:55 CEST] <furq> vp9 is already way too slow
[21:22:02 CEST] <ATField> Or youd have to hunt between each pair through various blogs and stuff?
[21:22:22 CEST] <Demon_Fox> AV1 takes from Daala, and Daala is supposed to be highly parallel
[21:23:03 CEST] <ATField> Also (by-the-by) vlc is supposed to support subtitles on vp9, but it doesnt seem to be able to.
[21:23:50 CEST] <Demon_Fox> vlc uses ffmpeg, which only supports some subtitles
[21:24:15 CEST] <Demon_Fox> h.265 really wasn't supposed to half the bitrate h.264
[21:24:27 CEST] <Demon_Fox> It's a bit closer to what xvid is to mpeg2
[21:25:50 CEST] <furq> https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding#History
[21:25:55 CEST] <furq> there are a few references to 50% there
[21:27:22 CEST] <Demon_Fox> and besides, h.265 or HEVC, will flop like mpeg4 part 2 (the standard xvid uses)
[21:27:54 CEST] <Demon_Fox> As mpeg4 part 2 had unrealistic licensing requirements like h.265
[21:30:33 CEST] <Demon_Fox> Which will probably demand something similar to "mpeg4 part 10" for h.265
[21:40:42 CEST] <Demon_Fox> furq, They rushed it, and it won't hit that mark
[21:40:54 CEST] <Demon_Fox> Not for quite some time
[21:41:38 CEST] <Demon_Fox> At least according to everything I read
[21:57:02 CEST] <furq> well yeah
[21:57:31 CEST] <furq> sadly a lot of people read that and take it at face value
[21:58:28 CEST] <furq> or think that a comparison between two reference encoders on selected source material is exactly equivalent to the difference between two real encoders on real material
[21:58:40 CEST] <furq> on all real material, even
[22:06:06 CEST] <nicolas17> I have two directories, each with a lot of .jpg frames, I want to make a video with all the frames from the first directory, then all from the second, *but* I want to apply a filter to the ones from the second
[22:06:51 CEST] <nicolas17> I guess I need two image2 streams, and I can apply a filter to one of them, but I don't know how to concatenate the results without making a temporary video file or something
[22:09:31 CEST] <furq> -i foo/img%02d.jpg -i bar/img%02d.jpg -filter_complex '[1:v] scale=640:480 [tmp]; [0:v][tmp] concat [out]' -map [out] out.mkv
[22:09:34 CEST] <furq> something like that
[22:09:49 CEST] <nicolas17> oh neat
[22:34:12 CEST] <wallbroken> so, any help?
[22:34:21 CEST] <wallbroken> i have a video and audio
[22:34:28 CEST] <wallbroken> but audio is a little faster than video
[22:34:40 CEST] <wallbroken> and in the end of video i get 2 mins of delay
[22:34:46 CEST] <wallbroken> in the center, maybe 1 minute
[22:34:48 CEST] <wallbroken> is linear
[22:34:55 CEST] <wallbroken> what can i do to fix that?
[22:37:27 CEST] <Demon_Fox> Did you convert the audio and the video at the same time?
[22:37:36 CEST] <wallbroken> no
[22:37:45 CEST] <wallbroken> i've taken the audio from another source
[23:20:26 CEST] <CoJaBo> What can I do to make ffmpeg blow thru an input file as fast as possible? E.g., just read the whole thing without actually doing anything
[23:21:14 CEST] <c_14> ffmpeg -i file.mkv -f null /dev/null
[23:21:47 CEST] <Mavrik> probably -codec copy as well :)
[23:24:15 CEST] <CoJaBo> It's actually faster without the -codec copy
[23:24:39 CEST] <c_14> faster with here
[23:25:40 CEST] <CoJaBo> Odd; I get about 550MB/sec without it, nearly half that with
[23:26:11 CEST] <Demon_Fox> wallbroken, Sorry it took this long, but that could be a real issue
[23:26:22 CEST] <wallbroken> c
[23:26:30 CEST] <wallbroken> c_14, do you have some suggestion?
[23:26:32 CEST] <Demon_Fox> audio is often stretched and etc
[23:27:14 CEST] <c_14> either atempo, or asetrate
[23:27:38 CEST] <wallbroken> what?
[23:27:46 CEST] <wallbroken> delay is linear
[23:27:51 CEST] <wallbroken> little at the start
[23:27:55 CEST] <c_14> those are filters
[23:27:55 CEST] <wallbroken> 2 minutes at the end
[23:27:59 CEST] <c_14> which make the audio play faster
[23:28:37 CEST] <c_14> Ie, if you have a 10 minute video and by the end of the video the audio is 1 minute ahead
[23:28:44 CEST] <c_14> then the audio is 10% faster than the video
[23:28:48 CEST] <c_14> therefore slow the audio down 10%
[23:30:26 CEST] CTCP SOUND: "jj.wav" from wallbroken (wallbroken!~wallbroke at unaffiliated/wallbroken) to #ffmpeg
[23:32:04 CEST] <wallbroken> c_14,
[23:32:17 CEST] <wallbroken> 40:59
[23:32:20 CEST] <wallbroken> 42:44
[23:32:51 CEST] <wallbroken> 42:44 is the viddeo
[23:32:56 CEST] <wallbroken> 40:59 is the audio
[23:33:09 CEST] <wallbroken> so i need to make 40:59 a little slow
[23:33:22 CEST] <wallbroken> to make it the same lenght of the video
[23:33:59 CEST] <c_14> My trusty pocket calcu^woracle tells me that you want -af atempo=0.959048
[23:34:07 CEST] <balrog> wallbroken: what was that ctcp sound about?
[23:34:57 CEST] <furq> CoJaBo: it depends what you mean by read the whole thing
[23:35:09 CEST] <furq> -c copy won't actually decode the streams
[23:35:29 CEST] <furq> which isn't much use if you want to check for errors or something
[23:35:35 CEST] <wallbroken> sorry it was a mouse error
[23:35:39 CEST] <wallbroken> ignore it
[23:35:58 CEST] <wallbroken> c_14, ok, and how to mux?
[23:36:18 CEST] <c_14> ffmpeg -i audio -i video -af atempo=0.959048 out.mkv ?
[23:36:24 CEST] <c_14> eh
[23:36:27 CEST] <c_14> +-c:v copy
[23:36:29 CEST] <Demon_Fox> The delay can only be fixed by stretching
[23:36:38 CEST] <Demon_Fox> and I'm not exactly sure how to do that
[23:38:05 CEST] <CoJaBo> furq: Ah, then I def. want to avoid that one anyway. Odd it's slower tho...
[23:41:20 CEST] <wallbroken> c_14, atempo what exactly does?
[23:41:34 CEST] <c_14> In this case makes the audio slower
[23:41:57 CEST] <wallbroken> ok, and if i need firstly to extract the video from another avi?
[23:42:24 CEST] <wallbroken> avi (audio, video) ----> mux: video + new audio
[23:43:20 CEST] <c_14> ffmpeg -i avi -i video -map 0:a -map 1:v -af atempo=0.959048 -c:v copy out.mkv
[23:43:50 CEST] <c_14> If the video has subtitles, other audio tracks you'll want to map those as well
[23:47:01 CEST] <wallbroken> c_14, and the audio?
[23:47:13 CEST] <c_14> what about it?
[23:47:19 CEST] <wallbroken> the sources must be: the video from an avi, and the audio from an mp3
[23:47:38 CEST] <c_14> ffmpeg -i mp3 -i avi -map 0:a -map 1:v -af atempo=0.959048 -c:v copy out.mkv
[23:49:04 CEST] <wallbroken> [matroska @ 03278a20] Can't write packet with unknown timestamp
[23:49:04 CEST] <wallbroken> av_interleaved_write_frame(): Invalid argument
[23:49:20 CEST] <wallbroken> i'm trying with .avi
[23:54:26 CEST] <wallbroken> c_14, looks good
[23:54:38 CEST] <wallbroken> look well synced
[00:00:00 CEST] --- Sun Jun  5 2016

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