[Ffmpeg-devel-irc] ffmpeg.log.20180728

[burek]

[00:24:31 CEST] <benbro> if I have X number of virtual cores on google cloud platform
[00:24:50 CEST] <benbro> transcoding from one format to hls will use all cores?
[00:25:27 CEST] <benbro> or maybe there is a point where it's a waste
[00:27:14 CEST] <Hello71> encoding is not embarrassingly parallelizable, no
[00:27:53 CEST] <furq> there are diminishing returns with more cores
[00:28:11 CEST] <furq> i assume this is for vod and not a live input
[00:28:39 CEST] <benbro> furq: yes, not realtime
[00:28:51 CEST] <benbro> I'm currently using 8 vCPUs
[00:29:13 CEST] <benbro> so I should compare encoding time of the same file with 4 cores?
[00:29:36 CEST] <furq> i expect it'll be slightly more than half as fast
[00:29:37 CEST] <benbro> Hello71: so it's not parallelizable?
[00:29:44 CEST] <furq> no it's parallelisable
[00:29:48 CEST] <Hello71> that's not what I said.
[00:29:52 CEST] <furq> right
[00:30:22 CEST] <furq> there are (somewhat) noticeable overheads involved in parallelising it
[00:30:31 CEST] <furq> which is why you get diminishing returns
[00:30:35 CEST] <benbro> so if 4 cores will take 10 minutes to transcode, 8 cores should be a bit more than 5 minutes?
[00:30:42 CEST] <furq> i would expect so
[00:30:51 CEST] <benbro> thanks
[00:31:04 CEST] <benbro> and what if top show that only 50% of the cpu work?
[00:31:14 CEST] <furq> then you've got a bottleneck somewhere else
[00:31:35 CEST] <benbro> where?
[00:31:41 CEST] <furq> shrug
[00:31:42 CEST] <benbro> I'm only using ffmpeg inside docker
[00:31:45 CEST] <furq> most likely decoding or filtering
[00:31:59 CEST] <benbro> not using filters
[00:32:04 CEST] <benbro> decoding is not multi-core?
[00:32:06 CEST] <furq> are you not rescaling
[00:32:32 CEST] <benbro> I am
[00:32:36 CEST] <furq> well yeah that's a filter
[00:32:38 CEST] <benbro> to 3 resolutions
[00:32:39 CEST] <benbro> ok
[00:32:54 CEST] <furq> the scale filter is singlethreaded so that's probably the culprit
[00:33:11 CEST] <benbro> maybe I should transcode all 3 resolutions in parallel
[00:33:15 CEST] <furq> yeah i was just typing that
[00:33:22 CEST] <benbro> cool. I'll try it
[01:28:11 CEST] <duriangray> does anyone know how to resolve this issue: RTMP_ReadPacket, failed to read RTMP packet header
[01:28:18 CEST] <duriangray> Invalid data found when processing input
[01:28:31 CEST] <duriangray> when i use ffmpeg to pull in a rtmp feed
[02:27:45 CEST] <duriangray> for some reason ffmpeg is working on my mac, but not on my ubuntu vps. any ideas?
[02:29:05 CEST] <DHE> going to have to be a LOT more specific than that
[02:32:05 CEST] <duriangray> ok i think it has to do with the version
[02:32:36 CEST] <duriangray> running apt-get install ffmpeg in ubuntu gave me ffmpeg version 2.8.14-0ubuntu0.16.04.1
[02:32:52 CEST] <duriangray> but on my mac ive got ffmpeg version 4.0 Copyright (c) 2000-2018 the FFmpeg developers
[02:33:42 CEST] <DHE> that is a rather old version...
[02:34:02 CEST] <tdr> unless your linux is pretty dated, you should get a 3.2.x or higher
[02:35:13 CEST] <duriangray> ya that was weird. im running ubuntu 16.04 on a scaleway vps
[02:35:25 CEST] <duriangray> anyways, compiling from source and hoping that resolves my issues
[02:35:32 CEST] <duriangray> spent all afternoon on this bug ugh
[03:12:49 CEST] <rasten33> good luck duriangray
[03:14:01 CEST] <DHE> even if it's not pretty dated, git version builds pretty well on centos6 (circa 2010 distro)
[03:17:01 CEST] <duriangray> Detected librtmp style URL parameters, these aren't supported by the libavformat internal RTMP handler currently enabled. See the documentation for the correct way to pass parameters.
[03:17:08 CEST] <duriangray> that is the new error i mgetting :(
[03:36:04 CEST] <duriangray> Anyone know what this is: Invalid UE golomb code
[03:55:40 CEST] <Soni> can I coredump ffmpeg, reboot, and load the coredump?
[04:06:16 CEST] <Soni> (for resumable conversions and stuff)
[08:07:54 CEST] <MeiR> Hey, I thought you guys might be interested in this blog by freenode staff member Bryan 'kloeri' Ostergaard https://bryanostergaard.com/
[08:07:54 CEST] <MeiR> or maybe this blog by freenode staff member Matthew 'mst' Trout https://MattSTrout.com/
[09:12:51 CEST] <eldritch1> Hey, I thought you guys might be interested in this blog by freenode staff member Bryan 'kloeri' Ostergaard https://bryanostergaard.com/
[10:57:40 CEST] <codebam> Hey, so I cut a clip in ffmpeg with -ss and -t. It plays fine using mpv, vlc, or other ffmpeg players but using the default Android media player the audio is off by nearly an entire second
[10:57:45 CEST] <codebam> how can I fix that?
[10:58:00 CEST] <codebam> I didn't re-transcode, it was a copy
[10:58:22 CEST] <codebam> I transcoded the audio to AAC though
[10:59:00 CEST] <JEEB> vlc doesn't use FFmpeg's mp4 reader though
[10:59:42 CEST] <JEEB> also another thing you could test is firefox's mp4 playback, which knowingly doesn't support some features, but still manages to keep A/V sync because it doesn't muck with the timestamps
[11:00:01 CEST] <codebam> JEEB: works in firefox
[11:00:23 CEST] <codebam> but the audio doesn't start for a second or so
[11:00:42 CEST] <codebam> so I'm guessing that's the issue, but why is FFmpeg doing that?
[11:01:06 CEST] <codebam> if you want, here's the video I'm referring to
[11:01:11 CEST] <codebam> https://cytube.nsupdate.info/clip.mp4
[11:01:18 CEST] <codebam> also it's funny lmao
[11:01:20 CEST] <JEEB> if you told it to copy the video then it can't really cut at anything else than random access points
[11:01:32 CEST] <JEEB> of course the audio not starting but later is funky
[11:02:14 CEST] <JEEB> you can try moving the -ss to the point of the video where the random access picture is at and see if it adds the "unnecessary"
[11:02:17 CEST] <JEEB> audio there now
[11:02:18 CEST] <codebam> JEEB: well yeah but shouldn't it get the audio time right?
[11:02:29 CEST] <JEEB> yes, but if that's "unnecessary" audio :D
[11:02:32 CEST] <codebam> wait what do you mean?
[11:02:38 CEST] <JEEB> if your cut point is later
[11:02:45 CEST] <codebam> so move it to where the audio cuts in?
[11:02:59 CEST] <JEEB> the video cut point (aka where it could cut the video)
[11:03:04 CEST] <JEEB> and thus the audio is not "unnecessary"
[11:03:12 CEST] <JEEB> I'm just guessing what ffmpeg.c does
[11:03:28 CEST] <codebam> oh, okay. how do I know what the cut point is?
[11:03:43 CEST] <codebam> is there some way for me to check what the nearest cutpoint is and cut at that?
[11:05:19 CEST] <JEEB> you can -show_packets with ffprobe I think and then filter for the "keyframe" flag? I don't remember the exact stuff
[11:05:45 CEST] <JEEB> but looking at the Firefox output you should be able to figure it out
[11:05:50 CEST] <codebam> oh okay, well anyways I'll keep moving it around until I get it
[11:05:55 CEST] <codebam> a few ms off won't hurt
[11:05:59 CEST] <JEEB> as in, how much "extra" video before the cut point it is
[11:06:07 CEST] <codebam> yeah exactly
[11:07:00 CEST] <codebam> thanks JEEB
[11:17:28 CEST] <JEEB> codebam: but basically what you're dealing with is that player not handling mp4 correctly most likely :)
[11:19:46 CEST] <codebam> JEEB: yeah lol, that's crazy that the android media player doesn't play mp4's properly
[11:20:10 CEST] <codebam> I fixed it by cutting it 2 seconds later
[11:20:12 CEST] <JEEB> for web streaming they just separated their player completely from mainline android because a lot of vendors wouldn't update
[11:20:27 CEST] <JEEB> https://github.com/google/ExoPlayer/
[11:20:33 CEST] <codebam> oh, interesting
[11:20:42 CEST] <JEEB> so now most android video streaming apps use that
[11:21:26 CEST] <JEEB> also I really like it when people seem to add FFmpeg features with the code somehow converted into java there
[11:21:27 CEST] <codebam> oh right okay, I wonder if the bug I'm seeing is in exoplayer or mediaplayer
[11:21:53 CEST] <JEEB> (without mentioning that the code originally is from FFmpeg)
[11:22:04 CEST] <codebam> JEEB: haha I see that with other things too. someone rewrote corelibs in java for a stupid homescreen launcher
[11:22:29 CEST] <codebam> I found out when I did rm -rf Downloads/* and it deleted all the files in /sdcard
[11:23:54 CEST] <JEEB> well rewriting is OK, it's just that usually it's stuff that you can compare to the original C :D
[11:24:04 CEST] <JEEB> like, you can clearly see the "inspiration"
[11:24:32 CEST] <codebam> ohh yeah
[11:25:00 CEST] <JEEB> and that's all OK, just that people generally don't mention what they've done
[11:25:21 CEST] <JEEB> they just present it as new, original code
[11:50:35 CEST] <hrvoje> alec: you're welcome, and don't blindly divide by 90000, follow Mavrik's advice :))
[12:38:07 CEST] <revi21> Hey, I thought you guys might be interested in this blog by freenode staff member Bryan 'kloeri' Ostergaard https://bryanostergaard.com/
[20:53:59 CEST] <Li> How can this command syntax modified to prevent/avoid original files overwritting  for z in '*mp4'; do ffmpeg -i $z -an -c copy $z;done
[20:55:10 CEST] <poutine> for z in '*mp4'; do ffmpeg -i $z -an -c copy "vidonly-${z}";done
[00:00:00 CEST] --- Sun Jul 29 2018