[Ffmpeg-devel-irc] ffmpeg.log.20180626

burek burek021 at gmail.com
Wed Jun 27 03:05:02 EEST 2018

[00:32:43 CEST] <WeiJunLi> ffmpeg -i input.mkv -pix_fmt yuv420p -f rawvideo - | vpxenc --codec=vp9 --good --cpu-used=2 --threads=8 --row-mt=1  --webm --tune-content=film --end-usage=q --kf-max-dist=250 --bias-pct=100  --cq-level=40 ----width=1920 --height=800 - -o test_vp9.webm
[00:32:58 CEST] <WeiJunLi> Im using that pipe but when i try to vlc test_vp9.webm
[00:33:15 CEST] <WeiJunLi> I have a `mkv demux error: cannot find KaxSegment or missing mandatory KaxInfo`
[00:33:34 CEST] <WeiJunLi> ffmpeg -i input.mkv -pix_fmt yuv420p -f rawvideo - | vpxenc --codec=vp9 --good --cpu-used=2 --threads=8 --row-mt=1  --webm --tune-content=film --end-usage=q --kf-max-dist=250 --bias-pct=100  --cq-level=40 --width=1920 --height=800 - -o test_vp9.webm
[00:33:35 CEST] <WeiJunLi> That's the right pipe
[00:33:50 CEST] <WeiJunLi> Anyone have an idea of what's missing on the cfg
[00:36:37 CEST] <wfbarksdale> does anyone know of a good way to recover an MP4 which has media data (mdat box) but no other meta information?
[00:37:14 CEST] <wfbarksdale> I have other videos encoded with the same camera, same frame rate and everything, so seems like i could reconstruct / copy the meta information so salvage?
[00:37:46 CEST] <wfbarksdale> interwebs is only turning up this recover_mp4.exe but hoping to find a linux/mac utility
[00:46:12 CEST] <Hello71> try prefixing your search with "open source"
[00:46:15 CEST] <Hello71> works pretty well
[01:50:10 CEST] <Cracki> wfbarksdale, if that files has anything other than the video stream, you might be out of luck
[01:50:18 CEST] <Cracki> the interleaving of the container would be lost
[01:50:45 CEST] <Cracki> there's a chance you can find patterns in the mdat box that hint at whether it's H.264 or AAC (or whatever codecs were used)
[01:51:38 CEST] <furq> there's a oss tool called untrunc
[01:51:45 CEST] <furq> but it has some weird dependency on internal libav headers
[01:51:50 CEST] <furq> so i can imagine it'll be a pain to build
[02:12:31 CEST] <nicolas17> https://trac.ffmpeg.org/wiki/Create%20a%20thumbnail%20image%20every%20X%20seconds%20of%20the%20video
[02:12:50 CEST] <nicolas17> thumbnails... if I get one image every N seconds, it will have to decode everything, which will be slow, so I want i-frames only
[02:13:12 CEST] <nicolas17> if I use the pict_type command shown there, it gets *every* i-frame
[02:13:48 CEST] <nicolas17> can I get "one image every N iframes" or "one image roughly every N seconds rounding to the nearest iframe"?
[02:18:03 CEST] <nicolas17> okay nevermind :| iframes in this video have terrible quality
[04:18:39 CEST] <ChChCherryBom> https://pastebin.com/tjBiNtqj
[04:19:07 CEST] <ChChCherryBom> im converting mkv/x264/dts to mp4/ac3/aac but I can't figure out how to specify number of audio channels with mapping like this
[04:22:50 CEST] <furq> ChChCherryBom: -ac:a:1
[04:23:58 CEST] <furq> also you can just do `for f` instead of `for f in "$@"`
[04:25:23 CEST] <ChChCherryBom> thanks
[04:25:31 CEST] <ChChCherryBom> is that still valid for an automator script?
[04:25:42 CEST] <ChChCherryBom> im passing in files as arguments not looping through a folder in terminal
[04:25:48 CEST] <furq> they do the same thing
[04:25:54 CEST] <ChChCherryBom> sweet
[04:25:56 CEST] <furq> `for f` will just iterate over all positional arguments
[04:30:55 CEST] <ChChCherryBom> does this look valid? https://pastebin.com/U3TxfZX5
[04:31:08 CEST] <ChChCherryBom> oh woops
[04:31:16 CEST] <ChChCherryBom> I need to change the audio
[04:31:50 CEST] <ChChCherryBom> https://pastebin.com/jpZYyMVA
[04:41:42 CEST] <furq> don't put language metadata on the video stream
[04:41:57 CEST] <furq> other than that, sure
[04:42:54 CEST] <ChChCherryBom> oh makes sense
[04:52:21 CEST] <nicolas17> why not?
[04:54:23 CEST] <furq> it generally doesn't make much sense
[04:54:34 CEST] <furq> but also because ffmpeg -map doesn't let you combine stream type and metadata selectors
[04:54:57 CEST] <furq> so if you have a bulk script that does -map 0:v -map 0:m:language:eng then you end up double mapping the video stream
[04:55:03 CEST] <furq> that's no fun
[04:55:52 CEST] <furq> but it's also just a weird thing to do unless you have multiple video streams
[05:13:09 CEST] <ChChCherryBom> one last question I think, I haven't been able to find any info on this
[05:13:24 CEST] <ChChCherryBom> when converting subtitles from say ass/srt to mov_text, how do I copy the forced flag
[05:14:59 CEST] <ChChCherryBom> if there is one
[05:21:54 CEST] <crazybit> vidstabdetect: is there any reason to use accuracy < 15 if video processing speed is not an issue?
[05:27:34 CEST] <crazybit> also, what is a "local measurement field" that's mentioned in docs vidstabdetect -> mincontrast?
[06:06:05 CEST] <nicolas17> how can I split a video into multiple segments?
[06:06:43 CEST] <nicolas17> not for hls/dash streaming... I just need to split the video
[06:54:17 CEST] <Cracki> nicolas17, -ss and -t
[06:54:39 CEST] <Cracki> behave differently in front and after -i
[06:55:07 CEST] <Cracki> be aware that "-c copy" would only be able to cut at keyframes
[06:57:14 CEST] <nicolas17> I found the 'segment' muxer, seems to work well
[13:41:47 CEST] <Blacker47> hello. i want apply some filters (like deinterlace and crop) to a few videos and safe relults as y4m and then concatenate them (later with a few still-image-snippets between) to a big file (and then encode it). but ffmpeg seems not to support concatenate y4m files - any ideas how I should do this?
[13:56:11 CEST] <anyvision> Hey guys, I'm looking for a way to copy an rtsp's stream original pts (if such information exists). I've tried to use -copyts and -ts mono2abs but to no avail (pts appears to be relative rather than absolute).
[14:09:01 CEST] <anyvision> Hey guys, I'm looking for a way to get an rtsp stream's original (absolute) pts. I've tried -copyts & -ts mono2abs but to no avail. I'm not sure this information even exists but if it does, how can I get it? thanks
[15:30:00 CEST] <konnex> hey guys, just wondering if you can use expressions like random(x) in the output filename? doesn't seem to work for me
[15:30:48 CEST] <BtbN> Use your shell for stuff like that.
[15:31:40 CEST] <konnex> hmm okay, just thought it would be possible, but thanks anyways =)
[15:36:07 CEST] <konnex> but what about this: I am outputting to hls and want the filenames to be uuids and not just counting up... any way to do this?
[15:54:29 CEST] <Celmor> does ffmpeg behave differently on SIGINT (Ctrl+C) than pressing q?
[15:54:48 CEST] <Celmor> using former I get "Exiting normally, received signal 2."
[17:00:21 CEST] <King_DuckZ> hi, I'm porting some old code that is adding some options into a dictionary - options like sc_threshold, coder, 8x8dct, b_strategy, b-pyramid... is there a list of all such options with their valid ranges and the default values?
[17:15:27 CEST] <furq> King_DuckZ: https://gitlab.com/qruf/x264settings/blob/master/settings.md
[17:15:56 CEST] <furq> and http://www.chaneru.com/Roku/HLS/X264_Settings.htm
[17:16:02 CEST] <furq> i think that's the most up-to-date one
[17:21:50 CEST] <King_DuckZ> furq: I need to know what the default would be tho, like if I didn't put b-pyramid in the dictionary I pass to avcodec_open2, what would it default to behind the scenes?
[17:23:02 CEST] <King_DuckZ> unless, is there a particular column I should be looking at, in your link?
[17:23:47 CEST] <Fenrirthviti> default is listed for every option in the second link
[17:24:15 CEST] <King_DuckZ> ahh sorry, it looked like one long link
[17:24:25 CEST] <Fenrirthviti> second link is probably better to use
[17:26:30 CEST] <King_DuckZ> it looks very useful, thanks!
[17:27:20 CEST] <King_DuckZ> btw when the second link says preset's default is medium, it's the "medium" column from the first link that applies, correct?
[17:34:46 CEST] <furq> right
[17:49:31 CEST] <saml> is nut file good?
[17:50:57 CEST] <atomnuker> sehr gut
[18:10:40 CEST] <King_DuckZ> when I do av_dict_get(my_dict, blah blah); will that automatically create the dictionary if my_dict is null?
[18:11:32 CEST] <King_DuckZ> or av_dict_set() does it maybe?
[18:29:32 CEST] <crazybit> besides ffmpeg source code and official docs, does anyone have a source for a more detailed explanation of vidstab filters?
[18:29:33 CEST] <acos> Are USB devices supported for video capture?
[18:31:42 CEST] <crazybit> acos: $ ffmpeg -devices
[18:33:11 CEST] <crazybit> acos: and yes you can, at least if you're on Linux
[18:34:55 CEST] <acos>  Coom. trying to capture old videos.  Almost got a pcie device
[18:35:28 CEST] <crazybit> you just need to know the /dev entry
[18:35:46 CEST] <bencoh> .59
[18:35:50 CEST] <bencoh> (woops)
[18:35:50 CEST] <crazybit> ffmpeg -i /dev/whatever
[18:35:59 CEST] <crazybit> beauty of Linux
[18:36:41 CEST] <crazybit> AFAIK you do have to tell ffmpeg what format it is though, so you would add -input_format mjpeg or whatever
[18:37:57 CEST] <crazybit> ^ actually i'm not sure that's required, maybe only for some types of hardware i don't know
[18:39:44 CEST] <acos> Hmmm its older
[18:39:50 CEST] <acos> Its not that good hardware.
[18:40:14 CEST] <acos> Might have to inline deinterlace
[18:48:04 CEST] <acos> What linux distro is best for ffmpeg? Can I live boot USB ubuntu?
[18:50:24 CEST] <crazybit> if you want the newest features, use a rolling release distro since it'll have the newest release of ffmpeg... if you don't care, it does not matter much so long as you don't use some outdated distro version
[18:50:34 CEST] <tdr>  acos running it from usb would work, but you'd need to find one that has it.
[18:50:45 CEST] <acos> Just want to capture like 60 tapes
[18:51:04 CEST] <crazybit> acos: don't use a usb live distro if you wan't to also use usb for capture
[18:51:17 CEST] <acos> Oh :( hmmm. I got more USB ports
[18:51:45 CEST] <crazybit> well ok
[18:52:10 CEST] <acos> I guess I can dial boot on this laptop
[18:52:24 CEST] <kepstin> just make sure the storage you're using and the capture device aren't on ports that share bandwidth (which is sometimes hard to tell)
[18:52:52 CEST] <acos> Well it will be a sata data disk
[18:52:58 CEST] <crazybit> acos: better yet, if you do boot distro via usb, boot it to memory if you have more than enough that way it won't use usb
[18:53:03 CEST] <crazybit> ah
[18:53:16 CEST] <acos> Hmmm 16gb ram in that laptop
[18:53:26 CEST] <kepstin> yeah, shouldn't be a problem if you're writing to a sata disk
[18:55:35 CEST] <acos> Hope so
[18:55:45 CEST] <acos> Not sure what format to save the video
[18:56:01 CEST] <crazybit> mp4 probably
[18:56:09 CEST] <acos> Kinda dont want h264
[18:58:20 CEST] <kepstin> don't use mp4 for live captures, it's unreadable if there's a crash during capture
[18:58:30 CEST] <kepstin> (mkv is good, you can always remux later)
[19:06:31 CEST] <acos> What's the data rate
[19:07:24 CEST] <kepstin> whatever you set it to when encoding
[19:07:28 CEST] <acos> Hmmm
[19:07:32 CEST] <acos> Not sure.
[19:07:47 CEST] <acos> What's datarate of uncompressed again?
[19:07:54 CEST] <kepstin> way too high
[19:08:10 CEST] <acos> Hmm. Ya not sure what settings to choose for this then
[19:08:13 CEST] <kepstin> well, if you're not sure, a good option is to use libx264 encoder with "-crf" mode, setting a value that gives you acceptable quality.
[19:08:46 CEST] <kepstin> (the default crf is 23, most folks think 18 is very high quality. lower numbers are higher quality)
[19:09:44 CEST] <acos> But I want to re edit this later.  Would hate generation loss of exporting h264.
[19:10:29 CEST] <kepstin> if you really want to avoid generation loss, consider using a lossless codec, e.g. ffv1 or x264 in lossless mode (option "-qp 0")
[19:12:21 CEST] <acos> Good idea.  Wish I could use dnhx
[19:12:34 CEST] <acos> I hear those are good intemrdite codecs
[19:13:03 CEST] <kepstin> most intermediate codecs are actually lossy
[19:13:27 CEST] <kepstin> they're usually designed as I-frame only (or very small gop) to make non-linear editing/cutting easier
[19:14:34 CEST] <kepstin> (i mean, not all, and some have both lossy and lossless modes)
[20:07:04 CEST] <furq> 18:07:47 ( acos) What's datarate of uncompressed again?
[20:07:22 CEST] <furq> acos: for reference, (bpp * width * height * fps) / 1024
[20:07:57 CEST] <furq> and probably / 1024 again because this is going to be in megabits per second
[20:08:13 CEST] <JEEB> bits are generally calculated in / 1000
[20:08:20 CEST] <JEEB> in video encoders etc
[20:08:25 CEST] <JEEB> so a kilobit is 1000 bits
[20:08:31 CEST] <furq> damn SI
[20:08:45 CEST] <JEEB> of course after you divide by eight and make into bytes, then you go into 1024 area again
[20:09:01 CEST] <bencoh> :)
[20:09:11 CEST] <furq> also you can find the bpp for your pixel format in ffmpeg -pix_fmts
[20:09:37 CEST] <acos> Hmmm thanks you smart
[20:09:56 CEST] <acos> Not sure what reisltuion vhs video tapes are 420x240?
[20:10:05 CEST] <furq> depends on your capture device
[20:13:26 CEST] <acos> It's some old USB thing
[20:13:38 CEST] <acos> With the yellow red white rca
[20:13:54 CEST] <im_dumb> SI is the worst thing since the imperial system
[20:16:06 CEST] <bencoh> I'd expect it to depend on pal/ntsc as well
[20:16:51 CEST] <acos> Ntsc
[20:16:55 CEST] <acos> Not in palland
[20:26:38 CEST] <ChChCherryBom> why does the duration of tracks change when I change the container from mkv to mp4?
[20:27:32 CEST] <kerio> with -c:v copy -c:a copy?
[20:30:22 CEST] <kepstin> acos: most capture devices will use the standard/typical size for the video standard, so you'll probably get an interlaced 720x480 signal from that.
[20:33:41 CEST] <ChChCherryBom> yes
[20:34:31 CEST] <ChChCherryBom> -c:v copy changes from 2:22:27:873 to 2:22:27:872 chapters go from :873 to :831
[20:36:13 CEST] <acos> Hmmm kepstin thanks
[20:36:30 CEST] <ChChCherryBom> subtitles go from :873 to 0:06:01:347 (being converted to mov_text, but that length is weird)
[20:40:28 CEST] <furq> .873 to .872 is probably just because of a different timebase
[20:40:44 CEST] <furq> not sure about the other stuff though
[20:41:16 CEST] <furq> are the subtitles actually desynced
[20:43:37 CEST] <ChChCherryBom> I need to try it on another set to see, I can't find the forced subs part
[21:04:29 CEST] <Hello71> VHS is analog though, isn't it? so theoretically you can get higher resolution than NTSC/PAL
[21:05:28 CEST] <Hello71> like, it doesn't technically have horizontal pixels, only lines
[21:17:45 CEST] <acos> Hmmm cool
[23:43:53 CEST] <Ars> Hi guys, pls help me.
[23:43:53 CEST] <Ars> I am transcoding and multicasting stream like: fmpeg RTMP_Stream   udp://
[23:43:53 CEST] <Ars> Also i have stream check script (ffprobe udp://, but when executing that command ffmpeg stops.
[23:43:53 CEST] <Ars> I understand there is port binding problem.
[23:43:53 CEST] <Ars> But how i can check that UDP stream alive or no? How to chek stream on udp:// ?
[00:00:00 CEST] --- Wed Jun 27 2018

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