[mythtv] Seg Fault in mediacodec

[David Engel]

On Tue, Jul 03, 2018 at 10:37:04AM -0400, Peter Bennett wrote:
> 
> 
> On 07/02/2018 09:38 PM, David Engel wrote:
> > On Mon, Jul 02, 2018 at 05:14:52PM -0400, Aman Gupta wrote:
> > > On Mon, Jul 2, 2018 at 3:58 PM Peter Bennett <pb.mythtv at gmail.com> wrote:
> > > > Hi Aman
> > > > 
> > > > Thank you for all your help so far.
> > > > 
> > > > I upgraded my Shield to Android 8.0. Now I get a seg fault every time I
> > > > play 1080 interlaced recordings. Progressive recordings are fine, and
> > > > 480 interlaced are fine. Also 4K recordings are fine. With 1080
> > > > interlaced it gets a seg fault in avcodec_receive_frame. This happens at
> > > > about the fifth frame received in the video. It starts off fine, with
> > > > avcodec_receive_frame returning EAGAIN until some number of packets have
> > > > been sent, then it receives a few frames, then there is a seg fault in
> > > > memcpy. There are no null addresses being passed to memcpy, but
> > > > something must be invalid. This was working fine with Android 7. I am
> > > > using the default buffer allocation: AVCodecContext->get_buffer2 =
> > > > get_avf_buffer. avcodec_receive_frame should allocate the buffers using
> > > > that routine so they should be valid.
> > > > 
> > > > [backtrace snipped]
> > > > 
> > > You can try the mpv-android apk from GitHub to compare. I'm pretty sure it
> > > works fine on Oreo.
> > mpv-android almost always crashes for me after a split second on 1080i
> > content.  When it doesn't crash, it just exits playback, also after a
> > split second.  720p content works fine, just like with MythTV.
> > 
> > David
> Thank you for doing that test.
> 
> This indicates the problem is somewhere in ffmpeg rather than mythtv code. I
> don't know what the trigger is, interlaced video or mpeg2 video, but it does
> not affect 480 interlaced mpeg2 video.

I have a few channels using 1080i and h.264 encoding.  It happens with
recordings from them as well.

Davi

> The issue of the illegal state exception while fast forwarding is still
> there so I should remove the code that discards frames, as that did not fix
> it consistently.
> 
> I will wait a while to see if FFmpeg can give us a fix, before looking into
> it further.
> 
> Peter

-- 
David Engel
david at istwok.net