Raw MPEG-4 Part 2 stream Q & A

[SeeMoreDigital]

I've been looking at the beta versions of Gspot (2.60 B00) and MediaInfo (0.7.4.0 BETA), both of which can read various information from raw/elementary (.CMP/.M4V) MPEG-4 Part 2 streams.

One bit of information neither application can reveal is the streams FPS speed... Can such information be extracted from elementary streams?


Cheers

[bond]

you would need to readout the VOL. you can do that with mpeg4vol when the stream is placed in mp4 ;)

[SeeMoreDigital]

Hmmm!

So are you saying it's not possible to determin the FPS speed of a RAW MPEG-4 Part 2 stream without placing it into a container first. Or that nobody has designed a tool to determin the FPS speed of a RAW MPEG-4 Part 2 stream?


Cheers

[bond]

nobody designed a tool

[SeeMoreDigital]

nobody designed a toolThat's more encouraging....


Thanks Bond

[Sergey A. Sablin]

nobody designed a tool
Elecard stream eye tool - http://elecard.com/products/products-pc/consumer/streameye-tools/
could determine real frame-rate from elementary mpeg-4 part 2 streams.

[SeeMoreDigital]

Elecard stream eye tool could determine real frame-rate from elementary mpeg-4 part 2 streams.Indeed it looks like it can...... but not at $600.00 LOL

[squid_80]

I'm curious; What practical reason would there be for doing this?

[SeeMoreDigital]

I'm curious; What practical reason would there be for doing this?For all us people who prefer to work with elementary streams (whether they be audio or video) it's important to have the facility to check the FPS speed of the elementary stream - just in-case you forget to make a note of it prior to de-muxing ;)

[bond]

For all us people who prefer to work with elementary streams (whether they be audio or video) it's important to have the facility to check the FPS speed of the elementary stream - just in-case you forget to make a note of it prior to de-muxing ;)hm, i am not sure whether that flag always contains the correct fps for being in sync with audio (but propably will)

[squid_80]

That's what I thought too. I know of scenarios where it can happen, but none of them are all that common. It would be easy to mod xvid_decraw to do it.

[SeeMoreDigital]

Sounds like a plan Squid...

Given the FPS speed can be obtained from RAW MPEG-1 and MPEG-2 streams, I think it would make sense to offer the same for RAW MPEG-4 streams too ;)

[squid_80]

It would be easy to mod xvid_decraw to do it.
Hmmm, I was wrong; when xvid decodes a VOL it only returns the width, height and PAR to the host program.

[GodofaGap]

Out of interest:

Can the VOL header contain a frame rate (in whatever form)? If frames already have timestamps, an additional frame rate would be quite confusing if the timestamps and frame rate are a mismatch (e.g. vfr).

[squid_80]

In the vol there's also a flag called fixed_vop_rate. I think if the stream is VFR this flag is set to 0 and one of the numbers used to derive the framerate is not present. On the other hand if fixed_vop_rate is set to 1 the framerate can be derived and if there are discontinuous timecodes the decoder should assume there is an error in the stream.

I might be completely wrong, I'm no expert.

[bond]

someone should read the specs! :D

[squid_80]

I find source code easier. It doesn't put me to sleep.