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| Random Accesible Partial MXF Files http://freemxf.org/forum/viewtopic.php?f=3&t=84 |
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| Author: | akira [ Sat Jun 16, 2007 6:27 am ] |
| Post subject: | Random Accesible Partial MXF Files |
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? |
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| Author: | Matt Beard [ Fri Jun 22, 2007 8:57 am ] |
| Post subject: | |
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) |
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| Author: | akira [ Mon Jun 25, 2007 6:19 am ] |
| Post subject: | |
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. |
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