freeMXF.org

Open discussion about freeMXF.org tools and MXF in general
It is currently Mon Dec 30, 2024 5:42 pm
Board index » MXF Categories » General MXF



Post new topic Reply to topic  [ 3 posts ] 
Author
Search for:
Message

Offline
Board User

Joined: Fri Jul 28, 2006 2:58 am
Posts: 10

Post Posted: Sat Jun 16, 2007 6:27 am 
Top  
I am cosidering how decoder can random access for partial mxf files.
If it parse klv packets, it can play only from top and it require OP-1a or OP-Atom or... some simple files.

Parsing klv packets in essence container areas is very slow.
If Partition Packs has parameter that indicate next partition, or size of essence container with last KLV Fill.

Encoder need to rewrite all footer parition position of partion packs, then easy to support to write next partition, or write RIP before header partition in Run-In area that match SMPTE-377M.

I did not read Generic Stream Partition 410M yet, I wish some good info from it.
Or Any method to get next partitions position?

 Profile  

Offline
Insider

Joined: Thu Apr 15, 2004 10:39 am
Posts: 198
Location: Scotland

Post Posted: Fri Jun 22, 2007 8:57 am 
Top  
There is a Seek() function built into BodyReader in MXFLib that does the work of locating a specified stream offset in an essence stream.

Give that a try if you need random access.

Because MXF is designed to be a) easy on the encoder and b) viable for streamed media (e.g. data tape) there is no way that you can have anything in the partition pack that requires knowledge of something significantly downstream in the file (such as how much essence will be in this partition - which may be hundreds of Gb)

 Profile WWW  

Offline
Board User

Joined: Fri Jul 28, 2006 2:58 am
Posts: 10

Post Posted: Mon Jun 25, 2007 6:19 am 
Top  
Thanks to reply Mr. Matt Beard.

And I have few question.

I recognize that there is no way to random access for general MXF.

I need to access partial file that lack latter part. ( from network problem )
But I want to access the exist data at least.
I know KLV parser is good solution for OP-1a files.

I will put index table information at system scheme items for recovery and streaming access without index table. Or I need to write complete index table segments in header partion.

I read SMPTE 394M, 405M ( SS-1 ) and 326M, 331M, 385M ( STDI-CP ).
And I chose SS-1 for this try.

Is first item of system scheme-1 the only one item in one Contents Package or in whole essence container ?
I want to write each frame information of index table segment to first item for simple structure.

I will write index table information ContentPackageIndexArray( for flags, key frame, and KLV Metadata Sequence( for PosTable information of index entry ).
But the document write that it is for clip or custom wrapping.
Is it ok ?

I have no information for system scheme from google.

Thanks to read.

 Profile  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

Jump to:  


Who is online

Users browsing this forum: No registered users and 6 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group :: Style based on FI Subice by phpBBservice.nl :: All times are UTC