NULL packets

[Mobileace]

Is the amount of NULL packets in the transport stream fixed? Is there anyway to find out how many much NULL packets are there?

[drmpeg]

Originally posted by Mobileace
Is the amount of NULL packets in the transport stream fixed? Is there anyway to find out how many much NULL packets are there?
The amount of null packets is variable depending on the Transport Stream bitrate
and the bitrates of the elementary streams within the transport. The amount also
varies in time. A nice graphical tool is TSReader Lite which can be downloaded here:

http://www.coolstf.com/tsreader/

If you need raw packet counts, you can use my demuxer which I've attached.

Usage is:

xport -pavtdszn <filename> <program number> <video stream number> <audio stream number>

Typically:

xport <filename> 1 1 1

Ron

[Mobileace]

Thanks for the program. but i suppose it can input a .mpg for analysis right? But why is it that i record a 10 sec video using my NOVA TV USB receiver and input it to the program for analysis. It is unable to read. The recorded video is in MPEG-2 format.

[drmpeg]

Originally posted by Mobileace
Thanks for the program. but i suppose it can input a .mpg for analysis right? But why is it that i record a 10 sec video using my NOVA TV USB receiver and input it to the program for analysis. It is unable to read. The recorded video is in MPEG-2 format.
I assume you mean TSReader Lite since my attachment has yet to appear. I downloaded
TSReader Lite yesterday, and it works fine on my test Transport Streams.

Does NOVA TV USB output MPEG-2 Transport Streams or MPEG-2 Program Streams?
TSReader Lite only works with Transport Streams.

Ron

[Mobileace]

Really thanks alot.. But when i record a MPEG 2 program stream(video & audio).. i dun seems to get a standard ES by using TMPEG demux. Any Demux program to recommend that i can use to separate my video and and audio source? I got no problem with the audio(MPEG 1 layer II) but the video got some problem..I wanted to create my own TS.But my system cannot create a multiple TV programme transport stream, it prompt me error known as video frames too long. Maybe any1 out there knows how to solve? I using Rohde & Schwarz software called Stream Combiner to help me create my own TS.

[drmpeg]

"Video frames too long" may have to do with the bitrate of the video versus the
selected Transport Stream rate. The selected Transport Stream rate has to be
higher than the combined video ES, audio ES, PES overhead and PAT/PMT rates.

For instance, let's say you have 4 Mbps CBR ES video and 384 kbps ES audio. A good
starting point would be 6 Mbps Transport Stream rate. You can trim it closer by looking
at how many null packets are in the multiplexed Transport Stream (your original question),
or by calculating each overhead value.

For VBR video streams, the TS rate should be higher than the peak video rate
(plus the audio, PES overhead and PAT/PMT rates).

Ron

[Mobileace]

Are you trying to tell me to increase the bitrate of my TS? I do not know if the TS creator software i have can do that or not. I think i got to play with the software to find if there is an settings that allows me to increase the rate. Hmm.. at least i have an idea on where the problem can possibly lies in..Thanks for all comments.. might need your help more in time to come.. hehe.. anyway thanks alot!!

[drmpeg]

Setting the TS bitrate is pretty fundamental. For instance, the US
ATSC TS rate is 19.392658 Mbps. If your tool doesn't support setting
the TS bitrate, it must be only for some very specific application.

You can download some demo TS muxers from Manzanita Systems that work
very well (but are restricted to 10 seconds of bitstream).

Single program:
http://www.manzanitasystems.com/products/mp2tsms.htm

Multi program
http://www.manzanitasystems.com/products/mp2tsmm.htm

Feel free to post questions for me on this thread. I work with MPEG-2
and Transport Streams professionally at LSI Logic (formerly C-Cube
Microsystems).

Ron

[Mobileace]

Thanks ron for being able to clarify my doubts. Actually, i am working on a project on DVB. My task is to be able to create my own TS and to be able to broadcast it through my school's DVB-T system. There is alot on MPEG-2 Standards that i need to know, but by just reading the standards alone can bring me far, i will definitely shoot questions to you in time to come..Thanks Thanks...

Calvin

[Mobileace]

ERROR : ES has wrong count of videoframes!
ERROR : ES can't be combined with TS!

This is the error i got! Do you think it got to do with datarate? The fact is that i want multiple program in a TS. Initially i only multiplexed 1 programme in the TS, i can worked, after that i tried to add another programme to the TS, making it to 2 programme in a TS. This is where the error will occur.One more thing, i already checked the software i am using, it does shows the datarate, but we are unable to change it and it is fixed!

Calvin

[jvmjm]

Hi, Is there a recommended value or a way to calculate the amount of null packets to use on a TS? What I had read is that null packets helps to fill the TS when no packets are available in order to keep a bitrate, correct me if I am wrong, please!!!

[DrP]

Since you plan on pushing your transport stream through your school's DVB-t system you will need to find out what the modulation parameters are in order to calculate the required packet rate. Once you have that you can work out how many nulls you need to insert. Since you are probably muxing variable rate video the task of exactly how many nulls to insert should be left up to your muxing software - ie, you tell it what bit rate the transport stream is supposed to be and let it do the rest.