[Ffmpeg-devel-irc] ffmpeg.log.20150324

[burek]

[00:54:32 CET] <kevmitch> using libswresample (from within mpv) converting (for example) 5.1 s16 to stereo float, is the downmixing done in float?
[01:57:05 CET] <hexagon5un> Hi all.  Anyone have a good solution (command line) for how to get a video to change speed during the run of the video?  Like one segment runs at 1x, then some at 2x, then back to 1x?
[01:58:19 CET] <hexagon5un> previously, I've tried with cutting the vid into segments and changing the speed per-segment, but the audio glitches when they're re-assembled
[01:58:54 CET] <hexagon5un> right now, I'm trying with the "sendcmd" filter, but I can't figure out how to use sendcmd with setpts.
[01:59:26 CET] <hexagon5un> is there an easier way?
[03:04:28 CET] <iphoneffmpeg> hey guys
[03:04:52 CET] <iphoneffmpeg> I have an issue with playing sound on quicktime player
[03:05:04 CET] <iphoneffmpeg> for videos created using ffmpeg
[04:27:28 CET] <kevmitch> iphoneffmpeg: what command is used to generate your files?
[07:57:14 CET] <kevmitch> using libswresample (from within mpv) converting (for example) 5.1 s16 to stereo float, is the downmixing done in float?
[08:46:40 CET] <Elirips> ramiro: uuh, you sure about named pipes not working on win?
[08:47:12 CET] <Elirips> They would work on linux?
[08:47:44 CET] <Elirips> ramiro: Because if I tell ffmpeg to write to a non-existring named pipe, like '\\.\pipe\foo.png' I see the expected error 'Count not open file .. '
[08:48:20 CET] <Elirips> And as for an app it should be no difference if it writes to a named pipe or a file I was hoping that things will work fine once I create the pipe
[08:53:22 CET] <Elirips> ramiro: Also I see Ticket #986, but this is all about reading from a named pipe (seeking problem), whereas I would be writting to it, well I'll see later
[08:56:27 CET] <Elirips> or last I could let ffmpeg write to standard-out using '-' and then maybe pipe that to my named pipe. something like 'ffmpeg -i mysource - | \\.\pipe\foo.png'
[09:37:08 CET] <arvind_> hi guys, going through ffmpeg, is there any algo or fixed conditions so that I can detect in how many formats my file is convertible
[10:52:25 CET] <klaxa> arvind_: pretty much all of them?
[10:52:54 CET] <klaxa> any audio file ffmpeg can read can be converted to any audio file ffmpeg can write
[10:53:01 CET] <klaxa> same goes for video
[10:55:00 CET] <ramiro> Elirips, named pipes on windows require the use of a different API call from Win32, which FFmpeg doesn't use
[10:56:10 CET] <arvind_> klaxa: yes ffmpeg would try to do that, so i would be making presets here ?
[10:56:55 CET] <klaxa> i don't understand your problem
[10:58:05 CET] <klaxa> can you explain it differently?
[10:58:19 CET] <arvind_> simply, I want to transcode to different flavors, is there anything in ffmpeg for eg. If I give it an flv file , with what supported codecs it will transcode it
[10:58:41 CET] <arvind_> flv to mp4, flv to mkv
[10:59:21 CET] <klaxa> you can just specify multipe output files like so: ffmpeg -i input.flv -c:v libx264 -crf 25 output1.mp4 -c:v libx264 -crf 21 output2.mkv
[11:00:11 CET] <Elirips> ramiro: I'm just writting tests to see if ffmpeg really needs those when it writes its output. If that fails, I'll try to let ffmpeg write to standard-out, and then I would pipe the standard out to my named pipe
[11:00:22 CET] <Elirips> But as the standard out is way slower than a named pipe..
[11:01:35 CET] <ramiro> Elirips, if you know how to program in C I can help you implement named pipes in FFmpeg
[11:03:25 CET] <Elirips> ramiro: I'm quite experienced in C++. C I try to avoid ;) But lets see, I'm working on some test-code
[11:03:48 CET] <Elirips> and I'm also a n00b in developing on linux - working on windows mostly
[11:04:21 CET] <arvind_> klaxa: ok  then , let me make some oprations. I will be back here with some results
[11:04:31 CET] <ramiro> you can develop for FFmpeg on windows too. it's just somewhat slower
[12:13:32 CET] <smo_> hi
[12:14:00 CET] <smo_> trying to build ffmpeg of chromium on osx got this errors : http://paste.ubuntu.com/10668205/
[12:14:04 CET] <smo_> an idea please?
[12:14:08 CET] <smo_> idear*
[12:14:24 CET] <smo_> no problems on linux or win with same sources
[12:53:57 CET] <smo_> removing hevc and aac3 and it works :/
[12:54:01 CET] <smo_> ac3
[14:54:16 CET] <Elirips> ramiro, do you still think that named pipes do not work on windows? I think they do. At least: I created a minimal c++ app that opens a named pipe on '\.\\pipe\foo.png' and reads data from there. I can see that data arrives if I call 'ffmpeg -i rtsp://mySource -r 1 -an -updatefirst 1 -y \\.\pipe\cam01.png'
[14:54:36 CET] <Elirips> okay, of course I do not know if the data that arrives makes sense or not..
[14:55:01 CET] <ramiro> '\.\\pipe\foo.png' or '\\.\pipe\cam01.png'
[14:55:58 CET] <Elirips> \\.\pipe\cam01.png
[14:57:36 CET] <ramiro> so you create the named pipe from outside. maybe that does work. ffmpeg is not able to create a named pipe
[15:11:28 CET] <Elirips> ramiro: yes, I create the named pipe in a differenct process (the one that needs the frames from ffmpeg)
[15:24:16 CET] <Elirips> so, maybe this is offtopic now, but anyway: I have success with ffmpeg piping its data into my named pipe. How can I detect the data "boundary" - I need to know when the next png-image starts (or even better, when one is finished)
[15:24:26 CET] <Elirips> Do I need to rely on some magic binary value?
[15:24:33 CET] <Elirips> that marks the start of a png file?
[15:54:45 CET] <spectromas> if I have a .mkv video that is 7gb with DTS 5:1 audio, how big would the video be (roughly) if I converted it the audio to mp3 V0 or ogg -q8, keeping everything else the same?
[15:56:23 CET] <Mavrik> spectromas, do an ffprobe on it
[15:56:25 CET] <Mavrik> check the bitrates
[15:56:46 CET] <Mavrik> good quality MP3 is going to be like 200-300kbit/s
[15:57:17 CET] <spectromas> Mavrik: that gives me Stream #0:1(eng): Audio: dts (DTS), 48000 Hz, 5.1(side), fltp, 768 kb/s (default)
[15:57:34 CET] <spectromas> I'm just not sure how to work out how much difference just the audio would make to the overall video size
[15:57:35 CET] <Mavrik> spectromas, yep, what's the length of the video?
[15:57:58 CET] <spectromas> Mavrik: 3 hours 48 mins
[15:58:31 CET] <Mavrik> ok, so - 3hrs48 = 13680s
[15:59:32 CET] <Mavrik> ((768 / 8) * 13680) / 1024) = 1280MB of audio track
[15:59:46 CET] <Mavrik> if you're MP3 is going to be an excellent 250kbit or so
[16:00:25 CET] <Mavrik> ((250 / 8) * 13680) / 1024) = 417 MB of audio
[16:00:32 CET] <Mavrik> so you save 800MB :P
[16:00:46 CET] <spectromas> excellent thank you Mavrik
[16:00:57 CET] <spectromas> not sure if it would be worth it then in that case
[16:01:07 CET] <Mavrik> it usually isn't since video dwarfs the audio
[16:01:08 CET] <spectromas> considering it would probably take to do
[16:01:13 CET] <Mavrik> which you can probably see in bitrates :)
[16:01:48 CET] <spectromas> great, thanks again Mavrik
[16:03:45 CET] <olivierrr> Hey guys, can't seem to get -shortest flag working properly
[16:04:03 CET] <olivierrr> http://pastebin.com/UtCKwYMJ
[16:04:19 CET] <justinX> I suppose it is possible to get just the mp3 bitrate out of ffprobe, so I can make statstics on what my mp3 collection have
[16:05:39 CET] <Mavrik> justinX, yep, also ffprobe has several output formats so you can easily automate it
[16:05:52 CET] <justinX> (probably most often 96kbit/s)
[16:15:30 CET] <justinX> the question is how to find out how to make it output the format you want?
[16:23:55 CET] <Mavrik> justinX, hmm?
[16:24:00 CET] <Mavrik> ffprobe -print_format json blah.mp3
[16:24:08 CET] <Mavrik> -print_format format  set the output printing format (available formats are: default, compact, csv, flat, ini, json, xml)
[16:26:01 CET] <justinX> ok
[16:40:27 CET] <justinX> of some strange reason all the output from ffprobe goes to stderr though. and -print_format doesn't really change output.
[16:42:05 CET] <justinX> except a { and the } line for json that goes to stdout :-D
[16:42:46 CET] <kepstin-laptop> justinX: you have to include some -show_* options to select what you want to include in the output
[16:43:10 CET] <kepstin-laptop> In this case, -show_streams is probably appropriate
[18:08:23 CET] <justinX> I bet that there must be some shorter way to produce a list of bitrates than what I wrote though
[18:10:23 CET] <justinX> find /media/username/D/music/ -name "*.mp3" > list.txt ;  mapfile -t mylist < list.txt ; for i in "${mylist[@]}"; do ffprobe -show_format "$i" 2> /dev/null |grep bit_rate |sed 's/bit_rate=//'; done
[19:37:16 CET] <Peace-> i got a weid audio problem here and i got this strange message http://paste.ubuntu.com/10671749
[19:37:27 CET] <Peace-> just compiled
[19:37:48 CET] <Peace-> i have a i7
[21:34:16 CET] <sagax> hi all!
[21:34:38 CET] <sagax> ffmpeg might use firewire device?
[21:35:10 CET] <sagax> for input or output ot both
[21:35:18 CET] <sagax> or*
[21:35:57 CET] <sagax> firewire = IEEE 1394
[23:13:53 CET] <sagax> i finded this https://www.ffmpeg.org/ffmpeg-devices.html#toc-iec61883
[23:14:37 CET] <sagax> but, wondering whether to use someone else has already this?
[00:00:00 CET] --- Wed Mar 25 2015