On Sat, Dec 20, 2008 at 6:11 PM, AliReza Khoshgoftar <[email protected]> wrote: > So, > Just to make sure I got it right: > > 1) "AVPacket"s may be longer than MPEG TS and MPEG ES, they may be some MPEG > ES packets concatenated together.
well I think mpeg ES is the whole encapsulated elementary stream itself which cannot really be defined as a packet. You have another format encapsulated within the mpeg ES stream (eg. mpeg2 video or mpeg2 audio frames). > 2) If I open an "mpg" file, containing an MPEG ES, and zero out some blockes > of 188 Bytes(the whole block, with no care of any headers), is it the same > as zeroing out "data" field of "AVPackets" when I open it using > ffmpeg(libavcodec) tools? > (It's my understanding of your very last sentences[highlighted] and I hope > it is correct) yes. but remember that 188 bytes is just an mpeg-ts packet, the pes packet is encapsulated within the mpeg-ts packet - thus the ts headers are stripped off and you won't see them in the PES packet. Markus > > > Thanks, > Alireza > > On Sat, Dec 20, 2008 at 11:05 AM, Markus Rechberger > <[email protected]>wrote: > >> >> An AVPacket can have a different size than a TS Packet. >> >> It's like a TS Packet with a certain ID comes in with a Packet start >> identifier, and following >> packets with the same ID have to be concatenated till the next packet >> with a Packet start identifier comes in. >> MPEG- SI/PSI Sections usually have the length defined including a >> crc32 number at the end. >> As for the mpeg2 elementary stream the stream needs to conform the >> specs of the corresponding codec. >> For example the mp2 audio header themself also define the length of >> the packet, the packets which are returned >> for an mp2 stream is 8 times as big as a valid mp2 audio frame with my >> examples. >> *Zeroing out packet data will zero out the ES packet*, ffmpeg strips off >> the TS header when concatenating >> the TS packets. >> >> regards, >> Markus >> _______________________________________________ >> libav-user mailing list >> [email protected] >> https://lists.mplayerhq.hu/mailman/listinfo/libav-user >> > _______________________________________________ > libav-user mailing list > [email protected] > https://lists.mplayerhq.hu/mailman/listinfo/libav-user > _______________________________________________ libav-user mailing list [email protected] https://lists.mplayerhq.hu/mailman/listinfo/libav-user
