[FFmpeg-devel] working with file descriptors on Android

[Alex Cohn]

Thanks Olivier,

Custom IO looks like a nice way to work around the protocol
limitations. Unfortunately, it cannot work with avio_open(), so the
API becomes trickier for end users.

Also, just like with pipes, I cannot reliably close the file
descriptor when ffmpeg execution is over, can I?

BR,
Alex Cohn

On Mon, Jul 27, 2020 at 11:01 AM Olivier Ayache
<olivier.ayache at gmail.com> wrote:
>
> A good alternative to work with FFmpeg on Android is Xuggler, it presents
> FFmpeg's API directly to Java/Kotlin.
>
> To deal with fd you can declare and implement your own IO handler by
> implementing
> https://github.com/olivierayache/xuggle-xuggler/blob/ffmpeg-3.x-dev/src/com/xuggle/xuggler/io/IURLProtocolHandler.java
>
> I currently maintain a fork which is fully working on Android (work in
> progress for iOS with Kotlin multiplatform).
>
> https://github.com/olivierayache/xuggle-xuggler
>
> Best
>
> Olivier Ayache
>
> Le dim. 26 juil. 2020 à 23:16, Alex Cohn <alexcohn at netvision.net.il> a
> écrit :
>
> > On Sun, Jul 26, 2020 at 10:21 PM Martin Storsjö <martin at martin.st> wrote:
> > >
> > > Hi,
> > >
> > > Without having too much opinion on the JNI stuff (direct access to
> > > content:// urls might be convenient, but on the other hand, it's not
> > > really something you'd end up with if using the command line tool on its
> > > own - if you have one of those you most probably have some java code for
> > > getting it anyway - as far as I remember...)
> >
> >
> > You are more than right, Martin.
> >
> > None of these approaches can work with a command line tool. Worse,
> > running a command line tool in the context of an Android app is
> > becoming trickier with every new release of the platform, and in this
> > case I cannot blame it on poor engineering. This happens because
> > Google tries to tighten the security on Android just as much as
> > possible.
> >
> > There is a nice cross-platform alternative, though.
> > https://github.com/tanersener/mobile-ffmpeg provides Java and
> > Objective-C APIs to run ffmpeg shared library "as if it were an
> > executable": it can receive the input as a string which mimics the
> > ffmpeg (and ffprobe) command line, and the output to stdout and stderr
> > is captured and passed back to the mobile app. In this scenario, it's
> > easy to get a `content:` URI by conventional Android SAF (structured
> > access framework) API in Java and pass it as string or as a derived
> > file descriptor (converted to string) to the command line parser that
> > will eventually call protocol->url_open().
> >
> > The latest release (Android Q a.k.a. Android 10, also API 29) made yet
> > another small step in this direction and caused lots of problems for
> > apps that rely upon file access by path. This was the incentive for me
> > to work on the ways to teach avformat to work with the `content:` URIs
> > correctly.
> >
> > BR,
> > Alex Cohn
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