[Ffmpeg-devel-irc] ffmpeg.log.20180827

burek burek021 at gmail.com
Tue Aug 28 03:05:01 EEST 2018

[10:43:23 CEST] <gaara4896> Hi, I was planning to write a steganography algorithm which require to modify some intermediate step of h264 to makes it works. Is ffmpeg suitable tools for the job?
[10:49:33 CEST] <furq> gaara4896: there's no builtin h264 encoder so probably not
[10:50:09 CEST] <furq> other than linking it with a modified x264 or openh264
[10:50:11 CEST] <JEEB> there's a bit stream filter for modifying H.264 bit streams
[10:50:21 CEST] <JEEB> so that can be utilized to making random changes
[10:50:39 CEST] <furq> yeah if you just want to pack data into the bitstream
[10:50:47 CEST] <furq> but i assume you want to actually modify the image somehow
[10:51:29 CEST] <furq> bye
[11:15:29 CEST] <haasn> the H264 bitstream should be roughly perceptually equal, right?
[11:15:47 CEST] <haasn> or, well, an ideal codec's bitstream would be
[11:15:53 CEST] <haasn> I wonder how far from this ideal real codecs are
[11:16:08 CEST] <haasn> i.e. does modifying a random bit in the bitstream have a consistent visual effect
[11:16:39 CEST] <haasn> I mean if you modify the DC offset you're going to have more of a visible effect than modifying some high frequency component
[11:16:54 CEST] <haasn> but how does this interact with quantization?
[11:17:09 CEST] <haasn> the bits that play a greater role should have more bits allocated to them, no?
[11:17:11 CEST] <haasn> in an ideal quantizer
[12:50:08 CEST] <Franciman> Hi
[12:50:22 CEST] <Franciman> How can I create a video stream with ffmpeg?
[12:50:40 CEST] <Franciman> Instead of writing the video to a file, I'd like to create a stream
[13:19:13 CEST] <BtbN> What kind of stream? Stream to an rtmp server?
[13:21:22 CEST] <Franciman> yes
[13:21:28 CEST] <Franciman> sorry I forgot to mention
[21:20:09 CEST] <yagiza> It seems there is no way to specify RTCP port when using SDP demuxer.
[21:21:22 CEST] <yagiza> And there is no way to play RTP with non-static payload type without using SDP demuxer.
[21:22:52 CEST] <yagiza> So, in most cases there is no way to specify an RTCP port to send packets when playing RTP media.
[22:33:06 CEST] <pi-> https://paste.pound-python.org/show/3sUzuJGRTko8j9gqQEd4/ <-- can anyone suggest what might be going wrong here?
[23:33:19 CEST] <LigH> Hi.
[23:35:18 CEST] <LigH> Can anyone help me with building issues related to pkgconfig files (*.pc)?
[23:35:48 CEST] <DHE> can you be more specific?
[23:38:24 CEST] <LigH> There is the "media autobuild-suite" which helps building ffmpeg in a regularly updated MSYS2 environment and with regularly updated sources of the ffmpeg project and related libraries.
[23:38:29 CEST] <LunaLovegood> Can I mix two audio channels into one (stereo -> mono) but give "priority" to one channel? Like that the left channel gets attenuated by 12 or so dB whenever there is some activity on the right channel (voice) ?
[23:38:40 CEST] <LigH> Recently, there was a preparation for liblensfun, but it was not finished.
[23:39:36 CEST] <LigH> I wanted to test it, I enabled the library to be included, it was downloaded, compiled ... and then there was a problem with the installation.
[23:40:04 CEST] <LigH> I found that instead of pkgconfig/liblensfun.pc, there is instead a file pkgconfig/lensfun.pc which was nor expected.
[23:40:47 CEST] <LigH> Now I wonder where the reason for this difference may be, if I shall "blame" the authors of lensfun for not sticking to any guidelines I do not even know about...
[23:41:33 CEST] <LigH> A pity that the author of the media-autobuild suite does not help in this case.
[23:41:43 CEST] <LigH> He said he has no time, no interest, etc.
[23:42:04 CEST] <LigH> So I'm trying to find anyone else with enough insight.
[23:43:29 CEST] <LunaLovegood> Oh, I think I can just boost the volume on the more important channel then use dynaudnorm before mixing.
[23:43:34 CEST] <LunaLovegood> right. sorrt.
[23:43:36 CEST] <LunaLovegood> *sorry
[23:46:18 CEST] <LigH> LunaLovegood: Sounds like a good idea to me.
[23:47:00 CEST] <LigH> But be careful with volumes, avoid clipping.
[23:47:42 CEST] <LigH> Often you want a dynamic compression (possibly with limiting), a loudness instead of a volume change.
[23:53:46 CEST] <LigH> DHE: Is that a topic for the devel channel?
[23:54:49 CEST] <JEEB> no
[23:54:55 CEST] <JEEB> it doesn't even have anything to do with FFmpeg
[23:55:11 CEST] <JEEB> also as far as I can tell people call their pkg-config .pc files however they want
[23:56:19 CEST] <JEEB> it's just that the name is generally to be static
[23:56:31 CEST] <JEEB> and defined by upstream unless upstream is stupid
[23:56:43 CEST] <JEEB> example http://up-cat.net/p/dd56369a
[23:59:03 CEST] <LigH> Means, someone would have to adapt the suite to this specific name. And I doubt I would be the one...
[00:00:00 CEST] --- Tue Aug 28 2018

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