Bit depth in the container format vs. in the output

[Arun Raghavan]

On Wed, 13 Jul 2016, at 07:08 PM, Carlos Rafael Giani wrote:
> Hello,
> 
> there is a problem with displaying file type information. Suppose I want 
> to show a file's bit depth on screen. The intuitive solution is to use 
> the caps that come out of a uridecodebin for example, and look at its 
> format value. But this can be misleading.
> 
> For example, if in a system, avdec_flac is used instead of flacdec, then 
> the format value will be S32LE even if the actual internal FLAC data 
> format is S24_32LE. So now all of a sudden the display shows "32 bit", 
> even though "24 bit" is more correct.
> 
> This is even visible with gst-discoverer. If you have a 24-bit FLAC 
> file, and run gst-discoverer-1.0 -v <flacfile> , the output with flacdec 
> present is:
> 
>      Channels: 2
>      Sample rate: 192000
>      Depth: 24
>      Bitrate: 0
>      Max bitrate: 0
> 
> but with flacdec missing (so only avdec_flac is available) it is:
> 
>      Channels: 2
>      Sample rate: 192000
>      Depth: 32
>      Bitrate: 0
>      Max bitrate: 0
> 
> So, the correct way to do this is to get the caps that *flacparse* 
> outputs, and not the decoder's. However, I have no clue how to do that, 
> or even how to communicate such information to the application properly. 
> There is no tag that can hold a GstCaps instance.
> 
> Any ideas?

At one point we had toyed with the idea of having a "shallow" mode in
GstDiscoverer -- basically get it to stop at the point of plugging a
parser. Perhaps this is worth resurrecting?

-- Arun