[Ffmpeg-devel-irc] ffmpeg.log.20180817

burek burek021 at gmail.com
Sat Aug 18 03:05:02 EEST 2018

[14:24:18 CEST] <kerio> is there a simple way with the ffmpeg commandline to crop the last column or row to get even sizes?
[14:28:25 CEST] <Nacht> if you want to say scale a video with 720p and have an even number of lines, I usually use scale=-2:720
[14:28:36 CEST] <Nacht> So I assume it can be done for crop as well
[14:28:38 CEST] <kerio> it's a bunch of gifs that i want to turn to mp4
[14:29:58 CEST] <Nacht> so you could use something like crop=in_w:-2
[14:30:52 CEST] <kerio> i need yuv420 because quicktime is dumb
[14:31:28 CEST] <kerio> looks like i can do floor(iw/hsub)*hsub:floor(ih/vsub)*vsub
[14:32:26 CEST] <kerio> well ok no i can't because i can't yuv420p before cropping so hsub and vsub are 1
[14:32:43 CEST] <kerio> but i can do floor(iw/2)*2:(ih/2)*2
[14:33:24 CEST] <kerio> this fucking ffmpeg man
[14:33:25 CEST] <kerio> it can do everything
[18:13:28 CEST] <kexec> hello, please, some recommendation for converting AVC 1080p to MPEG4 720x404? currently i have "ffmpeg -i in.mkv -c:v mpeg4 -vtag xvid -vf scale=720:-1 -qscale:v 3 out.avi"
[18:13:42 CEST] <kexec> if there is something i could make better
[18:13:51 CEST] <Cracki> no
[18:15:13 CEST] <DHE> just maybe you might want to look at actually using the xvid (3rd party) encoder. but mpeg4 should be compatible'
[18:15:43 CEST] <DHE> still, mpeg4 is old by today's standards
[18:16:37 CEST] <kexec> DHE: yeah, i know but this is for an older TV which cant play AVC.
[18:17:03 CEST] <kexec> and can i use the "qscale:v 3" also with xvid?
[18:17:28 CEST] <Cracki> consult the docs, then try it. if it doesn't work, ask again.
[18:18:09 CEST] <DHE> http://ffmpeg.org/ffmpeg-codecs.html#libxvid  <--- docs
[18:35:22 CEST] <white_gecko> hello, I'm trying to convet a opus file to apple lossless (alec) with "ffmpeg -i file.opus -c:a alex file.m4a" but I get the error "Unknown encoder 'alec'"
[18:35:29 CEST] <white_gecko> even though ffmpeg -codecs lists: "DEAI.S alac                 ALAC (Apple Lossless Audio Codec)"
[18:35:39 CEST] <JEEB> alec != alac
[18:35:41 CEST] <kepstin> white_gecko: you misspelled it
[18:35:46 CEST] <JEEB> it's not baldwin
[18:36:12 CEST] <kepstin> also, converting lossy to lossless is in general silly to do, but I guess if you want something to play on an apple device without losing more quality...
[18:41:38 CEST] <Cracki> and the command line contains yet another spelling, "alex"
[18:42:03 CEST] <Cracki> feature request: spelling correction for command line arguments
[18:53:46 CEST] <white_gecko> ah thenk you
[18:54:08 CEST] <white_gecko> thank you
[18:54:12 CEST] <white_gecko> sorry for that again
[18:54:31 CEST] <white_gecko> abviously I have some weakness here
[18:54:54 CEST] <white_gecko> so would it be a good idea to convert opus to aac then?
[18:56:11 CEST] <Cracki> no
[18:56:30 CEST] <Cracki> why would you?
[18:57:22 CEST] <white_gecko> because my A/V receiver does not support opus
[18:57:24 CEST] <white_gecko> https://www.onkyo.com/manual/txnr636/adv/en/074.html
[18:57:38 CEST] <Cracki> if it doesn't support opus, then of course you have to convert
[18:57:45 CEST] <Cracki> to something it DOES support
[18:58:07 CEST] <Cracki> in that regard, aac is one of the better choices
[18:58:32 CEST] <Cracki> vorbis is outdated.
[18:58:40 CEST] <Cracki> flac is a good choice because it's lossless.
[19:00:15 CEST] <white_gecko> ok so i go with aac
[19:00:19 CEST] <white_gecko> thanks again
[19:26:48 CEST] <kexec> please, any help with this? "[libxvid @ 00000178f7d8f940] Invalid pixel aspect ratio 40781/28687, limit is 255/255 reducing"
[19:27:21 CEST] <kexec> it repeats to infinity. command line: "ffmpeg -i "in.ts" -c:v libxvid -qscale:v 7 -c:a copy out.avi
[19:38:41 CEST] <kepstin> kexec: well, that should be an ignorable warning i think? But you can make it go away by using a setsar filter to fix the value
[19:38:54 CEST] <kepstin> what kind of input do you have with such a weird pixel aspect ratio?
[19:39:06 CEST] <kexec> kepstin: yeah, but it just repeats that warning and dont do anything
[19:39:37 CEST] <kexec> input:  Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p(progressive), 544x436 [SAR 40781:28687 DAR 221394:124819], 25 fps, 25 tbr, 90k tbn, 50 tbc
[19:40:19 CEST] <kepstin> wow, that's a really strange size. Is this a cropped part of some other video?
[19:42:55 CEST] <kepstin> anyways, assuming the source (before cropping) was widescreen standard definition pal, you want "-vf setsar=sar=64/45"
[19:43:37 CEST] <kexec> i am not sure, its a downloaded .ts. however, now i noticed that its being converted in fact, after pressing "s" its displays also the status line
[19:48:18 CEST] <kepstin> (or maybe it should be 16:11 instead, you'd have to check by looking at the video)
[19:50:02 CEST] <Cracki> people resample video like it's no big deal...
[19:50:26 CEST] <Cracki> "cropping" black borders off and rescaling to original size...
[20:02:42 CEST] <daddesio> Does ffmpeg currently support seeking with libaom? (e.g. the -ss flag.) I'm unable to use the , key in mpv because lavf is reporting "Seek failed (Operation not permitted)", and indeed, the -ss option doesn't work ("stockholm.ivf: could not seek to position 1.000").
[20:03:11 CEST] <daddesio> Here's how I compiled aom/ffmpeg/mpv: https://pastebin.mozilla.org/9091673
[20:03:38 CEST] <daddesio> mpv log when I use the , key: https://pastebin.mozilla.org/9091677
[20:04:14 CEST] <daddesio> And ffmpeg when I use the -ss flag: https://pastebin.mozilla.org/9091679
[20:04:39 CEST] <daddesio> ffmpeg can decode the file fine as long as I don't seek.
[20:22:21 CEST] <kepstin> daddesio: you'd want to put the video into a container with a seek index
[20:22:33 CEST] <kepstin> although I don't know what's supported right now for that
[21:44:11 CEST] <daddesio> I wonder if ffmpeg currently supports AV1 in another container (e.g. matroska)
[21:48:34 CEST] <kepstin> it looks like there's a defined way to store it in webm/matroska, but I haven't checked whether ffmpeg can do that. you could try building it from git if it's not in the 4.0 release.
[21:55:04 CEST] <kepstin> it looks like some recent version of mkvmerge has experimental support for av1
[22:16:23 CEST] <JEEB> kepstin: it's still not fully defined IIRC
[22:16:43 CEST] <JEEB> FFmpeg has now kind of support for the drafts for both mp4 and matroska, of which actually mp4 seems to be further
[22:17:19 CEST] <kepstin> daddesio: I have a better idea: seek to the frame you want before encoding in av1. That'll be way faster because you don't have to encode the video that comes before it ;)
[22:18:02 CEST] <kepstin> (i suppose it won't help if you're trying to debug an issue in the encoding of a particular frame in an existing video tho)
[22:18:26 CEST] <JEEB> so yea, I'd recommend with master FFmpeg to output into mp4 I guess :P
[22:18:29 CEST] <daddesio> yeah, for now I'll just decode to lossless (e.g. y4m or FFV1) ahead of time
[22:18:55 CEST] <JEEB> http://git.videolan.org/?p=ffmpeg.git;a=commit;h=8d5604a69aaa5e9ce6e930fcae6bab7e3f016841
[22:19:04 CEST] <kepstin> oh, is mp4 supported in ffmpeg now? that would work fine for this.
[22:20:15 CEST] <JEEB> just understanding that they're still more or less herping a derp around the exact structure of the extradata
[22:22:14 CEST] <kepstin> my experience with av1 is that I tried encoding a frame with it once, but didn't feel like waiting for it to finish.
[22:22:25 CEST] <kepstin> but that was a while ago
[22:44:48 CEST] <TD-Linux> daddesio, it currently supports av1 in mp4
[22:44:58 CEST] <TD-Linux> however it needs patches from the ml
[22:45:25 CEST] <JEEB> what james just pushed wasn't enough?
[22:45:33 CEST] <JEEB> (the one I linked)
[22:45:43 CEST] <TD-Linux> oh
[22:45:50 CEST] <TD-Linux> yeah that's good
[22:46:00 CEST] <TD-Linux> remuxing from ivf won't work yet though
[22:46:16 CEST] <TD-Linux> it needs a) my patch on the ml and b) a parser
[23:58:20 CEST] <Cracki> you keep talking about IVF... https://en.wikipedia.org/wiki/In_vitro_fertilisation
[00:00:00 CEST] --- Sat Aug 18 2018

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