Comment 6 for bug 1552245

> The problem appears to be that the metadata is encoded in the audio
> stream of a video. If there is no audio stream, there is no metadata.

That doesn't sound correct -- metadata is generally part of the container or a separate stream inside the container, rather than being handled at the codec level.

I don't have a krillin to test on, but the hardware codecs on arale don't seem to like dog.mp4:

    $ gst-discoverer-1.0 dog.mp4
    Analyzing file:///home/phablet/Videos/dog.mp4
    [Err, h264_dec_init] Fail to open Vdec Drv H264 instance! -11
    [Err] Error code -10
    [Err, h264_dec_deInit] Invalid input argument
    [Err] Error code -1
    Done discovering file:///home/phablet/Videos/dog.mp4
    An error was encountered while discovering the file
     GStreamer encountered a general supporting library error.

The same command on my amd64 desktop succeeds (which would presumably be using the ffmpeg/libav based software codecs).

As for the file not showing up, rebooting the device or restarting mediascanner-service will cause it to show up. This quirk is a known issue we need to fix that was introduced when moving the metadata extractor out of process. We should be inserting the placeholder entries in the index immediately in this case.