[linux-dvb] PES question

[Felix Domke <tmbinc@gmx.net>]

I have a small question i cannot solve by reading the mpeg-specs..

it must be a stupid error or something, but i can't see it.

On Video-PIDs we got a PES-stream.

this PES-stream consists, as the name says, of packets which all got a
PES-header.
a PES-packet is distributed over multiple TS-packets, since it's normally
longer than 184 bytes.
every ts-packet which contains the first part of the PES-packet has the
payload_unit_start_indicator set, and has often an adaption field inside the
TS-header (althought it's not required, and can be anywere else).

Now here's such a TS-packet as a hexdump: (please note that this packet is
not created by the dvb-s, so it isn't regenerated or stuff.. it SHOULD be as
plain as it comes out of the frontend)

47             Sync byte
41 FF          pusi_flag set, PID 0x1FF
30             adaption_field_control=3, cc=0
07             ok, we got an adaption field: adaption_field_length=7
10 0F 59 A5 9F 7E B1  ... the adaption field ...
00 00 01 E0    a PES stream startcode (0x1E0), 1110 xxxx means video, so
it's video stream 0
00 00          the packet_length
85 80 13 21 7A CF 86 FD FF FF FF FF FF FF FF FF FF FF FF FF FF FF
00 00 01 00 00 1F FF FB B8   ... and the ES ....
00 00 01 B5 87 57 5B DD 80
00 00 01 B2 44 54 47 31 41 F8 00 00 00 00 00 00 00 00
00 00 01 01 4A 58 08 0B 2C
00 00 01 02 4A 58 08 0B 2C
00 00 01 03 4A 58 08 0B 2C
00 00 01 04 4A 58 08 0B 2C
00 00 01 05 4A 58 08 0B ...


so, my problem is, WHY is the packet_length ZERO?

i tested it on several transponders, channel et al, it's always zero, which
makes the parsing of the next header very hard (if you have a PES which has
no pusi-flag anymore...)

the only  possible explanation i found was that 00 00 in fact means 1 00 00,
but i cannot really believe this (would mean PES-packets > 64k)

otherwise it would mean that some part of the receiver hardware modifies
this, but i can't believe this anyway..

bye,
felix domke



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