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Problems with Dolby Audio and typefind

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Problems with Dolby Audio and typefind

Neil Jones
17 posts
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 ?

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:

/GstPipeline:pipeline0/GstTypeFindElement:typefindelement0.GstPad:src: caps = video/mpeg, systemstream=(boolean)false, mpegversion=(int)4, parsed=(boolean)false

If I try to demux the file with qtdemux it fails, so i don't think the file is in an MPEG container, MediaInfo just shows it as an E-A3 file.

This is with version 0.10.x

Cheers,

Neil

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Re: Problems with Dolby Audio and typefind

Michael Smith
2 posts
On Thu, Dec 6, 2012 at 6:52 AM, Neil Jones <[hidden email]> 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.

Mike
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Re: Problems with Dolby Audio and typefind

Neil Jones
17 posts
> here's already an iec958 plugin, does that not handle it?

No that only supports formating AC3/DTS data into iec958 frames for transmission to a spdif sink, not the other way around.

Ok, once I find the time I'll try putting together some patches.

Neil


On Thu, Dec 6, 2012 at 6:48 PM, Michael Smith <[hidden email]> wrote:
On Thu, Dec 6, 2012 at 6:52 AM, Neil Jones <[hidden email]> 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.

Mike
_______________________________________________
gstreamer-devel mailing list
[hidden email]
http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel


_______________________________________________
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[hidden email]
http://lists.freedesktop.org/mailman/listinfo/gstreamer-devel