Problems with Dolby Audio and typefind

Michael Smith mlrsmith at
Thu Dec 6 10:48:18 PST 2012

On Thu, Dec 6, 2012 at 6:52 AM, Neil Jones <neiljay at> wrote:
> Hi,
> Im having issue with typefind correctly detecting Dolby audio.
> AC3:
> If im using a normal big-endian ac3 file then typefind works, but if I try
> capturing AC3 from a spif input the data is little-endain and has big chunks
> of zeros in it (as its transported as 2 channel 48Khz 16bit PCM accross
> spdif), typefind and aacparse fail to recognise this audio, if i manually
> pipe this audio into my decoder (with out gstreamer) it plays it fine.
> Should typefind / aacparse be able to deal with this data ? I had considered
> writing an iec958-src component which detect the incoming data type PCM /
> AC3/ DTS and strips out the zeros, has anyone done anything like this ?

There's already an iec958 plugin, does that not handle it?

I'm not sure how detectable (without a lot of false positives) that
format is - if I'm wrong about that, implementing a typefinder for it
sounds great.

> EAC3:
> I cannot get typefind to detect eac3 files correclty at all, using the dolby
> test sample 'eac3sample12.eac3' from dolby conformance test suite as an
> example (I can probably upload this somewhere once i check its ok to do so),
> it reports the file as:

Probably nobody had enough sample files to implement this properly.
You should write a patch to typefind to add an appropriate typefinder
for this.


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