[FFmpeg-devel] [PATCH 1/1] This change adds an encoder for Camera metadata motion. This is a type of sensor data associated with video, such as GPS, acceleration, gyro, and camera orientation. It does not encode video itself, but rather, this metadata.

[wm4]

On Wed, 12 Jul 2017 22:42:36 +0200
Hendrik Leppkes <h.leppkes at gmail.com> wrote:

> On Wed, Jul 12, 2017 at 8:31 PM, Louis O'Bryan
> <louiso-at-google.com at ffmpeg.org> wrote:
> > On Wed, Jul 12, 2017 at 9:16 AM, Louis O'Bryan <louiso at google.com> wrote:
> >  
> >> On Wed, Jul 12, 2017 at 12:50 AM, wm4 <nfxjfg at googlemail.com> wrote:
> >>  
> >>> On Tue, 11 Jul 2017 16:17:33 -0700
> >>> "Louis O'Bryan" <louiso-at-google.com at ffmpeg.org> wrote:
> >>>  
> >>> > If I need to write a new atom under stsd for my stream in the mov muxer
> >>> > <https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/movenc.c>
> >>> > (mov_write_stsd_tag),
> >>> > is it appropriate to indicate that through the AVStream metadata rather
> >>> > than the codec_tag?  
> >>>
> >>> It seemed to have lots of unrelated changes, but maybe I'm missing
> >>> something. If those codec tag refactors are needed, they should
> >>> probably be split into a separate patch.
> >>>
> >>> But it looks like most of those changes were unintended (Moritz
> >>> suspected that too). The tag addition itself is probably fine.
> >>>
> >>> Also, please don't top post on mailing lists.
> >>> _______________________________________________
> >>> ffmpeg-devel mailing list
> >>> ffmpeg-devel at ffmpeg.org
> >>> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >>>  
> >>
> >> That file had unrelated changes that shouldn't have been there, please
> >> ignore them.
> >> Now that there is no codec associated with the stream, there shouldn't be
> >> a codec tag at all, I would assume. (Another issue I need to deal with is
> >> that the MOV muxer also doesn't support streams without a codec, but that
> >> is separate.)
> >>  
> >
> > My goal is to modify the MOV/MP4 muxer so that I can mux the new stream
> > with video and audio streams. Part of that is writing a new sample entry
> > box under the stsd box.
> > Since I no longer plan to use an encoder for the stream, I was wondering if
> > the AVStream::metadata
> > <https://www.ffmpeg.org/doxygen/3.2/structAVStream.html#a50d250a128a3da9ce3d135e84213fb82>
> > would be an appropriate way to recognize that stream. Other cases in the
> > mov_write_stsd_tag function use the codec tag.
> > I have the following sample of that idea here, which allows me to use the
> > new stream and write the sample entry box:
> >  
> 
> You can associate a codec to the stream, put the codec in the data
> codec range. You just wouldn't have an encoder for it.
> This should probably work without any special hacks, I would guess.

If it does, I would assume it uses ffmpeg.c's stream copy path?

I still don't understand where the data comes from. Having a dummy
encoder that consumes dummy AVFrames would also require a dummy
decoder. Unless this is for something outside of ffmpeg.c.