Private stream in MPEG

[dil]

Hi,

How can i identify the format of the private_stream1? I expect dolby & PCM audio on private_stream1 other than VBI streams.

Thanks in advance
Dil

[kieranrk]

You use the descriptor in the PMT to find out.

[dil]

Thanks kieranrk for ur reply.

You use the descriptor in the PMT to find out.
Is it the correct way. I mean, will respective descriptor present all the time in PMT?
ISO 13818-1 tells registration_descriptor is used to identify private_streams, but i never saw it in PMT. Does it come in any of the other tables? Will this be present all the time?

[drmpeg]

The value of stream_type in the PMT can be used for some formats. If the value is greater than or equal to 0x80, then it's usually some specific format. For example, AC-3 is stream_type 0x81.

If the stream_type is 0x6, then there could be anything in the stream. For this stream_type, there will usually be a descriptor present in the PMT.

[dil]

If the stream_type is 0x6, then there could be anything in the stream. For this stream_type, there will usually be a descriptor present in the PMT.

Can u brief me what kind of descriptor i should look for?

[drmpeg]

You should look for a registration_descriptor. For example, the registration_descriptor format_identifier for SMPTE 302M audio is 0x42535344 ("BSSD" in ASCII).

Decoders like VLC definitely look for a registration_descriptor if the stream_type is 0x6.

Here's a list of format_identifier values.

http://www.smpte-ra.org/mpegreg/mpegreg.html