[Ffmpeg-devel-irc] ffmpeg.log.20130327

[burek]

[01:44] <Jordan_> what happens if you try to encode a higher frame rate than the source
[01:51] <llogan> Jordan_: ffmpeg will duplicate frames to attempt to reach your desired output frame rate
[02:04] <Jordan_> what would be the point in that?
[02:09] <llogan> for example if you have image inputs that you want to decode at a certain frame rate but your outputencoder or container  may only suport certain frame rates
[03:38] <Demon_Fox> Anyone know how to take the first couple seconds out of a video into a new file for tests?
[03:38] <Demon_Fox> not like dd
[03:40] <klaxa> ffmpeg -i <input> -ss 10 -c copy <output>
[03:40] <klaxa> copies the first 10 seconds in a new file
[03:40] <klaxa> copies all codecs, skips attachments though
[03:40] <Demon_Fox> what does -c do?
[03:41] <Demon_Fox> oh
[03:41] <klaxa> codec
[03:41] <Demon_Fox> thanks
[03:41] <Demon_Fox> I wanted to do some tests with high motion scenes using x264 to know how high to set the crf
[04:57] <bigmac> im looking to batch process a large list of movies... each video may already exist as different size's and formats (700mb.avi to 2000mb.mp4 etc)... the end result i would like to be a smaller file size for a droid phone
[04:58] <bigmac> i struggle to produce these results
[05:09] <relaxed> bigmac: figure out which libx264 -crf value looks good and fire away
[05:11] <relaxed> bigmac: a slower -preset will yield better compression
[05:35] <bigmac> relaxed: im not sure of this -crf... maybe a example you can show me a example?
[14:36] <alal> Hello
[14:36] <alal> I have a problem with decoding an mp3 flow and would like to ask if anyone can check what could be wrong with it
[14:37] <alal> http://listen.radionomy.com/Remzouille-Radioo
[14:37] <alal> it is a web radio
[14:37] <alal> When I open it in Chrome it seems to work (although there is a noise for the first 1s)
[14:42] <alal> Thanks in advance for any hints
[16:57] <gormux> hi all
[16:57] <gormux> I'm searching infos on hardware encoding, and there are not many as it seems
[16:58] <gormux> anyone uses vdpau or other piece of hardware to do the encoding with ffmpeg ?
[16:58] <retard> i didn't even know vdpau could do encoding
[17:00] <gormux> hum, maybe not vdpau, but it seems it is supported by vaapi, at least with intel
[17:08] <Mavrik> gormux, short answer: not supported by ffmpeg
[17:08] <Mavrik> :)
[17:10] <gormux> raaah, I want a solution :p
[19:01] <johnny_|_> Hey. How can I check if h264_vda is working. I have nvidia 8800gt and os x 10.7.3. I have ffmpeg with --enable-vda flag and ffmpeg -codecs | grep h264 outputs: DEV.LS h264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (decoders: h264 h264_vda ) (encoders: libx264 libx264rgb )
[20:01] <schtinky> so I know you can cat two or more MPEG-TS streams together... wondering if it's possible to also directly extract still frames from MPEG-TS without ffmpeg
[20:01] <schtinky> I assume not as the stream is still motion encoded and therefore is not a series of still frames
[20:02] <schtinky> can anyone confirm/deny?
[20:03] <ubitux> concat demuxer maybe?
[20:03] <ubitux> https://ffmpeg.org/faq.html#How-can-I-concatenate-video-files_003f
[20:07] <Mavrik> schtinky, well you do have to decode the stream :)
[20:07] <schtinky> ok that's what I was looking for
[20:07] <Mavrik> schtinky, only I-frames are encoded fully, others are motion encoded :)
[20:07] <Mavrik> ability to concat means that the container is flexible enough to alow that :)
[20:08] <Mavrik> nothing more
[20:08] <schtinky> how often to i-frames occur?
[20:08] <Mavrik> well... as often as the guy encoding your stream set it
[20:08] <schtinky> how do I find out?
[20:09] <schtinky> (also, iframes sounds like Apple's competitor to google glass)
[20:09] <schtinky> just throwing that out there
[20:09] <Mavrik> :D
[20:10] <Mavrik> schtinky, depending on format... for MPEG-2 usually mediainfo shows I-frame interval (as "GOP size")
[20:10] <Mavrik> for H.264 it can be arbitrary, but mediainfo can show parameters
[20:10] <Mavrik> you can also use ffmpeg's "frameinfo" filter to see how often they showup
[20:11] <Mavrik> also, I've used "StreamEye" software at work to show me that info
[20:11] <Mavrik> schtinky, usually it's about once per second for TV-streamed TS and much rarer on everything else
[20:11] <schtinky> interesting
[20:11] <schtinky> so in theory, given a TV mpeg-ts stream, I should be able to directly extract i-frames
[20:12] <Mavrik> yeah, but you still need to decompress them :)
[20:12] <schtinky> you said "encoded fully", if it's an image, what format is that?
[20:12] <schtinky> it's no longer MPEG-TS, it's what, png? jpeg?
[20:13] <Mavrik> um, it's something else :)
[20:13] <Mavrik> MPEG formats have their own way of encoding images
[20:15] <schtinky> ok thanks for the help mavrik. it's getting more complicated than it needs to be. I'll just use ffmpeg. I assume ffmpeg extracts images in the most efficient way possible anyway
[20:15] <Mavrik> that's correct :)
[20:15] <Mavrik> schtinky, what's your usecase?
[20:15] <schtinky> grabbing still frames from ATSC TV signal
[20:16] <schtinky> hardware encoder grabs in MPEG-TS
[20:16] <Mavrik> ah, on what interval?
[20:16] <johnny_|_> Hi. I am on OS X 10.7.3, nvidia 8800 GT and I get: "[h264_vda @ 0x&.]Failed to init VDA decoder: -12473.". Is it because outdated hardware?
[20:16] <schtinky> using ffmpeg to grab a frame every second, wondering if I could just grab them raw
[20:16] <schtinky> apparently not
[20:16] <Mavrik> schtinky, nah, just decoding the stream and grabbing frame each second is ok
[20:16] <Mavrik> schtinky, look at "select" filter
[20:16] <Mavrik> to filter them out and just set png output or something
[20:18] <schtinky> ok it's not computing yet. I'm using image output with %3d.jpg (or similar) and it's taking quite a bit of CPU
[20:18] <schtinky> are you saying select can do it more efficiently?
[20:18] <schtinky> when you say "them" what is "them"? The iframes? Or my once-per-second frames?
[20:19] <Mavrik> schtinky, "select" basically just (heh) selects frame by the criteria you choose and throws away everything else
[20:19] <Mavrik> schtinky, so if you set it to select one frame every second
[20:20] <Mavrik> you won't have to save 25 PNGs each second :)
[20:20] <Mavrik> which will be noticable on your CPU
[20:27] <schtinky> mavrik, whoa, that filter gave me tons of iframes
[20:29] <schtinky> ffmpeg -i test0.mpg -vf "select=eq(pict_type\,I)" /hoozon/test/%3d.jpg
[20:29] <schtinky> that just gave me 2200 images for a 10-15 second video
[20:30] <schtinky> oops, 38 seconds, but still
[20:30] <Mavrik> huh? that seems unlikely
[20:30] <Mavrik> you couldn't have more than a 1000 frames in 38 secs
[20:30] <schtinky> and they're all very pixelated
[20:31] <schtinky> you can make out what it is, but it's like encoding at 100kbps or something
[20:31] <schtinky> that's the quality
[20:31] <durandal_1707> because of jpg output
[20:31] <Mavrik> schtinky, well you're not setting jpeg quality anywhere ;)
[20:31] <Mavrik> use qscale parameter
[20:32] <schtinky> ah, right
[20:32] <Mavrik> schtinky, qscale 0 being best, 31 worst
[20:32] <schtinky> but why 2200 frames?
[20:32] <Mavrik> no idea :)
[20:34] <schtinky> changed it to png, still wrote 2200 frames. That's an SSD killer :)
[20:34] <Mavrik> ;)
[20:34] <schtinky> high quality, though
[20:35] <durandal_1707> png is lossless (slow zlib compression)
[20:37] <schtinky> http://pastebin.mozilla.org/2251415
[20:37] <schtinky> and yes, it's the yum version
[20:37] <schtinky> packaged, I mean, whatever
[20:41] <Mavrik> um, for some reason ffmpeg created 2200 duplicate frames O.o
[20:41] <Mavrik> 68fps input video? :)
[20:42] <ubitux> try to -vsync cfr
[20:43] <ubitux> -vsync vfr sorry
[20:43] <ubitux> Mavrik: see https://ffmpeg.org/trac/ffmpeg/ticket/1644
[20:43] <ubitux> well, schtinky actually.
[20:49] <schtinky> nice, I got 2 frames per second, high quality, huge reduction in CPU
[20:49] <schtinky> any idea why 2 frames per second, though?
[20:50] <Mavrik> becuase the video has 2 I-frames per second? :)
[21:21] <Smashcat> Hi, id ffmpeg==avconv ?
[21:21] <Smashcat> *is
[21:26] <Smashcat> Ok thanks. So they should take the same arguments I guess. avconv is crashing out while trying to create an h264 video from images (ubuntu 12.10 here). I'll see if I can get a copy of ffmpeg and see if that can do it
[21:28] <Smashcat> The error is "This stream was generated by a broken encoder, invalid 8x8 inference". And it helpfully generates a video of 0 bytes size :)
[21:28] <Mavrik> there are subtle differences in arguments and implementation
[21:28] <Mavrik> I suggest you ask people on #libav
[21:28] <Smashcat> ok thanks
[22:31] <i_s> i'm trying to build an old version of ffmpeg, and i'm getting this error: No rule to make target `libavcodec/hpel_template.c', needed by `libavcodec/dsputil.o'. Stop.
[22:32] <i_s> anyone know what is wrong?
[23:46] <Picola-GR> hello is there a way to append the output of ffmpeg to a file?
[23:46] <Picola-GR> like for example convert file1, file2 and concat both files into file3
[23:49] <klaxa> http://ffmpeg.org/trac/ffmpeg/wiki/How%20to%20concatenate%20%28join,%20merge%29%20media%20files
[23:49] <klaxa> Picola-GR: ^
[23:50] <Picola-GR> thanks
[00:00] --- Thu Mar 28 2013