[FFmpeg-devel] [PATCH] lavf: add ffprobe demuxer

[wm4]

On Thu, 22 Sep 2016 18:50:27 +0200
Stefano Sabatini <stefasab at gmail.com> wrote:

> On date Sunday 2016-09-18 15:28:45 +0200, Stefano Sabatini encoded:
> > On date Saturday 2016-09-17 18:42:35 +0200, Paul B Mahol encoded:  
> > > On 9/17/16, Stefano Sabatini <stefasab at gmail.com> wrote:  
> > > > On date Sunday 2016-09-04 23:25:56 +0200, Michael Niedermayer encoded:  
> > > >> On Sun, Sep 04, 2016 at 06:24:37PM +0200, Stefano Sabatini wrote:  
> > > >> > From: Nicolas George <george at nsup.org>
> > > >> >
> > > >> > With several modifications and documentation by Stefano Sabatini
> > > >> > <stefasab at gmail.com>.
> > > >> >
> > > >> > Signed-off-by: Nicolas George <george at nsup.org>
> > > >> > ---
> > > >> >  doc/ffprobe-format.texi  | 130 ++++++++++++++++
> > > >> >  libavformat/Makefile     |   1 +
> > > >> >  libavformat/allformats.c |   2 +
> > > >> >  libavformat/ffprobedec.c | 397
> > > >> > +++++++++++++++++++++++++++++++++++++++++++++++
> > > >> >  4 files changed, 530 insertions(+)
> > > >> >  create mode 100644 doc/ffprobe-format.texi
> > > >> >  create mode 100644 libavformat/ffprobedec.c  
> > > >>
> > > >> this seems not to apply cleanly
> > > >>
> > > >> can i pick this from some git repo ? (should work better than patch
> > > >> with unavailable ancestors)  
> > > >
> > > > Updated, this should apply cleanly on master.  
> > > 
> > > Why we need this hack?  
> > 
> > My use case: I need to inject a metadata stream using the ff*
> > tools. Metadata must be specified in a textual format. I already
> > designed and implemented the fftextdata format, but that was regarded
> > too limited.
> > 
> > Example:
> > ffmpeg -i input.mp4 -copyts -i data.ffprobe -map 0:v -map 0:a -map 1:0 -codec:d copy input+data.ts
> > 
> > With this format we allow to cover my use case, and it provides a more
> > generic format for such purposes (since you can specify multiple
> > streams). Also, it's inspired by the ffprobe output, so it can be used
> > together with ffprobe (via simple text editing) to generate files
> > which can be edited and feed to ffmpeg.
> > 
> > It would be possible to use any binary format for injecting the
> > metadata, but this approach is not very scriptable. Alternatively a
> > custom program to convert a custom textual format to any binary format
> > we support, but this would imply an additional step I want to avoid.
> > 
> > That said, if someone want/can propose an alternative path to this I'm
> > very open to suggestions.  
> 
> Ping. I'd like to commit this if there are no objections. Also,
> possibly add a muxer to generate output directly readable by the
> demuxer (this way we don't need ffprobe for generating the output, and
> we avoid the ordering issue).

I'm sorry to jump in as a nay-sayer, but it looks like a quite fishy
concept and I still don't get why it's supposed to be needed. The
documentation also doesn't say what this is supposed to be useful for.

It's also potentially a security issue (lots of text parsing, and can
construct inputs which might be tricky for API users).

I probably can't stop you from pushing this, but at least it shouldn't
be enabled by default.