[Ffmpeg-devel-irc] ffmpeg.log.20140313

[burek]

[09:18] <termos> When using libav across multiple threads, is there a list of any pitfalls I should look out for?
[09:56] <k0bi> is it posible to extract img and audio from rtmp stream and build it on site Synchrony
[10:20] <kvz> Can I tell ffmpeg to discard streams it doesn't understand? I have a file with 3 streams, 2 of which it doesn't understand. I would like it continue with the one it does. Here's the paste: http://pastebin.com/DhGgFkbL
[11:44] <relaxed> kvz: ffmpeg -i input -map 0:v:0 ...
[11:46] <kvz> relaxed: I'm looking for a syntax where I can leave out streams based on codec. I think the proposed syntax hardcodes by stream index & type = video?
[11:47] <kvz> relaxed: because sometimes people throw files at the same command, that have a perfectly sane video #0:1 stream. and by applying -map 0:v:0 now that one is lost. Correct?
[11:51] <relaxed> you would have to script it
[12:16] <kvz> relaxed: ok, thank you!
[13:16] <steinchen> hello all.. i have a mxf file with 8 mono audio channels... i need it in stereo.. have channels 1 and 3 to left and right stereo
[15:59] <asten> Hi. I have a question on h264 decoding process. Is it a good place to ask?
[15:59] <average> asten: well.. ask the question
[15:59] <average> asten: if someone knows, and they have time to answer you, and if they want to answer you.. if if if if if , then you'll get an answer
[16:00] <asten> http://stackoverflow.com/questions/22382040/h264-cavlc-decoding-coeff-token
[16:51] <srcreigh> hello
[16:58] <srcreigh> I have a question about configure flags.
[16:58] <srcreigh> I'm trying to compile FFmpeg minimally so that I can do h264 encoding to mp4.
[16:58] <srcreigh> Here's my current configuration: http://pastebin.com/dz12JL36
[16:59] <sacarasc> You disabled ffmpeg?
[17:00] <srcreigh> I'm using av* libs in C code directly.
[17:00] <srcreigh> With that configuration, avformat_alloc_output_context2(&outputCtx, NULL, "mp4", filename); results in a null output context.
[17:01] <srcreigh> Sorry, I should have said "I'm trying to compile av* libraries to do h264 mp4 encoding"
[17:02] <Zeranoe> Is there any encoder faster than mjpeg
[17:04] <Zeranoe> I feel like there are no good status for encoder speed or even quailty with modern hardward and modern codecs. I might need to fill that void
[17:07] <srcreigh> Update: I just compiled FFmpeg without the --disable-everything flag, and it worked!
[17:07] <srcreigh> Well, the code ran, Which is good. I still would like to minimize the build.
[17:11] <srcreigh> I just need to figure out which ./configure flags to pass in after --disable-everything to enable h264 encoding and mp4 muxing.
[17:44] <jarainf> srcreigh, why don't you use libx264 to encode whatever you are encoding?
[17:44] <jarainf> as in: not using ffmpeg at all
[17:46] <srcreigh> jarainf: I haven't looked at using libx264 directly. FFmpeg's muxing.c is a really great example for encoding as far as I can tell.
[17:46] <sacarasc> Because they want the MP4 muxing.
[17:47] <srcreigh> jarainf: also what sacarasc just said
[17:47] <srcreigh> and my project already has ffmpeg, so why not continue using it if it supports libx264
[17:48] <srcreigh> My question is really about mp4 muxing, I'm pretty sure that --enable-libx264 will give me h264 encoding.
[17:48] <srcreigh> --enable-muxer=mp4 doesn't seem to be enough for avformat to give me an mp4 output context for whatever reason.
[17:49] <Zeranoe> srcreigh: Your stripping the libs?
[17:49] <srcreigh> Zeranoe: yeah
[17:52] <Zeranoe> In my experience, it isn't easy to single out a single component to be compiled
[17:53] <srcreigh> Well, I've already done it for mp4/h264 demuxing and decoding. as you can see from the pastebin I sent here
[17:53] <srcreigh> (http://pastebin.com/dz12JL36)
[18:01] <srcreigh> I wonder if it's possible to make some kind of documentation for lib stripping.
[18:03] <srcreigh> Or get some logs that will say, like, "[avformat_alloc_output_context] OPENING MUXER foo"
[18:37] <llogan> Zeranoe: rawvideo, libx264, huffyuv, mpeg2video is faster. probably a bunch of others too.
[18:37] <llogan> mpeg4
[18:37] <Zeranoe> it seems that for very low latency it preforms well, better than x264 -crf 0
[18:38] <llogan> i assumed encoding speed
[18:38] <Zeranoe> yes
[18:52] <srcreigh> test
[19:20] <Zeranoe> How is does ffmpeg encode to gsm? I tried -c:a libgsm -f gsm file.gsm, and -c:a libgsm -f gsm out.wav
[19:24] <geqsaw> hi, I want to grap a video from my webcam, but my cpu is not fast enought to encode it with x264 in real time, and withoud encoding I get huge files. Which codec should I use to get relatively small videos without too much cpu load?
[19:25] <srcreigh> geqsaw: When I tried a bunch of different encoding formats yesterday, flv seemed to be very fast
[19:26] <llogan> flv is a container format. do you mean the flv1 encoder? that's old and shitty.
[19:26] <Zeranoe> ffmpegs first
[19:27] <llogan> geqsaw: use a pastebin site to show the complete output of: ffmpeg -f v4l2 -list_formats all -i /dev/video0
[19:27] <llogan> assuming /dev/video0 is your actual input name
[19:27] <Zeranoe> assuming your on Linux
[19:29] <srcreigh> well, whatever encoder you get from ffmpeg guessing an encoder by filename for "foo.flv"
[19:29] <srcreigh> was about an order of magnitude faster than foo.mp4
[19:29] <srcreigh> (I was playing around with muxing.c yesterday)
[19:29] <llogan> the defalt encoder can depend on how your ffmpeg was configured
[19:29] <Mavrik> geqsaw, you can control CPU use/quality tradeoff by using presets
[19:29] <llogan> for example, ffmpeg will use libx264 for flv, and if that is not available then it will use flv1
[19:30] <geqsaw> http://pastebin.com/Ksh99E84
[19:30] <srcreigh> llogan: huh, that's interesting. I had libx264. I wonder why the mp4 format was so much slower than flv.
[19:30] <llogan> i'm not sure. i'm also only familiar with the cli tool.
[19:31] <llogan> geqsaw: i was hoping your device would already provide H.264 video so you can simply stream copy, but i guess not.
[19:32] <Zeranoe> llogan: Do you know if there can be a IO bottleneck with the steam size of rawvideo?
[19:32] <Zeranoe> or is it not *that* big
[19:33] <llogan> you can test with: ffmpeg -i input -map 0:v:0 -c:v rawvideo -f null -
[19:33] <Zeranoe> and look for dropped frames?
[19:34] <llogan> geqsaw: what kind of hardware do you have that can't encode 640x480 (or smaller) fast enough?
[19:34] <llogan> Zeranoe: you can look at the encoding speed with null, and then compare it to a local file output and see if there is much of a difference
[19:34] <geqsaw> llogan: I have a intel i5 @ 1.8 Ghz dual core
[19:37] <Zeranoe> whats the container for rawvideo
[19:38] <Zeranoe> and is rawvideo bascially just the decoded stream?
[19:39] <geqsaw> I do not have a abnormal output, only after a few seconds the cpu is at 100% and ffmpeg is freezing for a couple of seconds...
[19:41] <llogan> then without any command and output i can only recommend to "use git head" for x264 and ffmpeg
[19:45] <geqsaw> llogan: with "git head" you mean the latest version of ffmpeg from github?
[19:46] <llogan> the latest from git://source.ffmpeg.org
[19:46] <llogan> and make sure to use yasm
[20:55] <lifeofgu_> is there any trick to compile ffmpeg for intel atom cpus?
[20:55] <lifeofgu_> on intel i7 ffmpeg is using all cores/threads, on intel atom it is only using one core/thread
[21:23] <mankan> Hi all. I've been tweaking x265 encoding to include vps/sps/pps before every keyframe and I wonder what would be suitable config parameter to enable this mode?
[21:48] <gers4302> I'm muxing multiple audio / video files. Everything seems to work fine with the output in VLC, but in WMP or QuickTime, it messes up. I'm getting encoded packets and using av_write_frame to write it back out. If the audio files doesn't start for 10 seconds, WMP will just start playing the audio right away. Is there a proper way to write frames that are offset using av_write_frame?
[00:00] --- Fri Mar 14 2014