16 replies to this topic

[MeanMachine]

Hello,

 

I'm trying to dump the raw TS of a DVB-C signal using the add-on tuner in Formuler F4 turbo. Following is the command executed and its result.

dvbsnoop -s ts -tsraw -b > /media/usb/raw.ts

Error(22): DMX_SET_PES_FILTER failed: : Invalid argument

How should this be interpreted? Will I be able to dump raw TS using this setup?

 

Regards

[athoik]

Νο,

You can't record all pids.

You need professional equipment or cheap USB sticks that support "record all pids".

Although you can record lot of pids. Use dvbsnoop pidscan to get them and then specify as many as you can of them.

[MeanMachine]

dvbsnoop pidscan does not seem to show any output!

root@formuler4turbo:~# dvbsnoop -s pidscan
dvbsnoop V1.4.53 -- https://github.com/PLi-metas/dvbsnoop

---------------------------------------------------------
Transponder PID-Scan...
---------------------------------------------------------
root@formuler4turbo:~#

Do I need to tune anything in any specific manner? What am I missing?

[MeanMachine]

Apparently this is because dvbsnoop is not finding any PIDs. Do I need to pass it any special option considering that F4 Turbo receiver is a combo tuner model? I'm trying to scan the tuner B (DVB-C). Does OpenPLi need to be tuned to a specific channel?

 

Pardon my lack of knowledge; I'm new to this field of satellite and cable TV equipment.

[Pr2]

Don't you need to specify which tuner to use in your dvbsnoop command line?

[MeanMachine]

Don't you need to specify which tuner to use in your dvbsnoop command line?

 

Indeed, I'm trying to google on the same lines, but haven't figured it out yet. /dev/dvb/ has only adapter0, and I think there should be adapter1 too. Why might this be? I'm able to scan, tune and watch TV channels on tuner B (DVB-C) without any issues.

PS: I'm using OpenPLi 6.2 release 20190507 by the way.

[Pr2]

I have a done a test on my Solo4K and without specifying the tuner it seems to give you the details of the currently running service.
I have test this to retrieve the PAT values:
 
dvbsnoop -n 1 0x00
 
I test on DVB-S2 and DVB-C.

[MeanMachine]

Thanks for the test Pr2.

 

I played with it a bit more. I'm getting pretty funny and inexplicable results by executing the following command. Every time it finds different PIDs!

dvbsnoop -s pidscan -pd 9

So far I have found the following PIDs after multiple random executions of the command.

[SECTION: DVB CA message section (EMM/ECM)]
.
.
.

[scrambled]
.
.
.

[SECTION: Program Map Table (PMT)]

[SECTION: Network Information Table (NIT) - actual network]
[SECTION: Service Description Table (SDT) - other transport stream]
[SECTION: Event Information Table (EIT) - other transport stream, present/following]

I can think of following possible reasons behind this behavior:

1. Issue with OpenPLi implementation or the drivers provided by Formuler
2. Faulty add-on DVB-C tuner module
3. Unreliable dvbsnoop implementation
4. Sporadic or very low frequency transmission of various PIDs by the broadcaster.

My knowledge in this area is very preliminary, so none of the above might be the real problem. What might be the situation here?

Edited by MeanMachine, 13 May 2019 - 14:14.

[athoik]

You can specify the demuxY, frontendX and adapterW on dvbsnoop.

Use lsof | grep adapter0 to identify the devices in use.

[MeanMachine]

Thanks athoik. Even though I would have expected adapter1 to be there for tuner B, dvbsnoop seems to somehow work out the currently running service as mentioned by Pr2 in the post #7. See my post #8 above, the result of pidscan is different for each execution of dvbsnoop! So the problem seems to lie somewhere else.

[MeanMachine]

Thanks for the test Pr2.

 

I played with it a bit more. I'm getting pretty funny and inexplicable results by executing the following command. Every time it finds different PIDs!

dvbsnoop -s pidscan -pd 9

 

Here is what I found on dvbsnoop examples page. Copying it here as this reference might help someone else later on.

 

 

The following output is an example of wrong decoding.
This is because the firmware of the dvb hardware is blanking the scrambling indicator bits in the transport stream packets, when passing these to the user application (e.g. dvbsnoop). This is bad behavior, but unfortunatly dvbsnoop is not able to detect this.

The pids from 0x00FF to 0x09FF are mostly video- and audio pids, but will be wrongly displayed as ATSC, DSM-CC, User-private, or whatsoever... 8(

 

It's unfortunate if this is indeed what's happening with the pluggable DVB-C tuner on Formuler F4 Turbo. I'll give cheap USB stick a try as suggested by athoik in post #2.

[Erik Slagter]

If pidsnoop doesn't work, just inspect the SI tables (like PAT and PMT).

Edited by Erik Slagter, 14 May 2019 - 18:33.

[MeanMachine]

If pidsnoop doesn't work, just inspect the SI tables (like PAT and PMT).

 

I liked the portmanteau Erik: pidscan + dvbsnoop = pidsnoop!

 

The command suggested by Pr2 in post #7 gives the PAT. How can I obtain the PMT?

root@formuler4turbo:~# dvbsnoop -n 1 0x00
dvbsnoop V1.4.53 -- https://github.com/PLi-metas/dvbsnoop

------------------------------------------------------------
SECT-Packet: 00000001   PID: 0 (0x0000), Length: 68 (0x0044)
Time received: 
------------------------------------------------------------
  0000:  00 b0 41 01 d5 e7 00 00  a9 d4 e1 00 a9 d5 e1 01   ..A.............
  0010:  a9 d6 e1 02 a9 d7 e1 03  a9 d8 e1 04 a9 d9 e1 05   ................
  0020:  a9 da e1 06 a9 db e1 07  a9 dc e1 08 a9 dd e1 09   ................
  0030:  a9 de e1 0a a9 df e1 0b  a9 e0 e1 0c a9 e1 e1 0d   ................
  0040:  87 15 80 6b                                        ...k

PID:  0 (0x0000)  [= assigned for: ISO 13818-1 Program Association Table (PAT)]

Guess table from table id...
PAT-decoding....
Table_ID: 0 (0x00)  [= Program Association Table (PAT)]
section_syntax_indicator: 1 (0x01)
(fixed): 0 (0x00)
reserved_1: 3 (0x03)
Section_length: 65 (0x0041)
Transport_Stream_ID: 469 (0x01d5)
reserved_2: 3 (0x03)
Version_number: 19 (0x13)
current_next_indicator: 1 (0x01)  [= valid now]
Section_number: 0 (0x00)
Last_Section_number: 0 (0x00)

    Program_number: 43476 (0xa9d4)
    reserved: 7 (0x07)
    Program_map_PID: 256 (0x0100)

    Program_number: 43477 (0xa9d5)
    reserved: 7 (0x07)
    Program_map_PID: 257 (0x0101)

    Program_number: 43478 (0xa9d6)
    reserved: 7 (0x07)
    Program_map_PID: 258 (0x0102)

    Program_number: 43479 (0xa9d7)
    reserved: 7 (0x07)
    Program_map_PID: 259 (0x0103)

    Program_number: 43480 (0xa9d8)
    reserved: 7 (0x07)
    Program_map_PID: 260 (0x0104)

    Program_number: 43481 (0xa9d9)
    reserved: 7 (0x07)
    Program_map_PID: 261 (0x0105)

    Program_number: 43482 (0xa9da)
    reserved: 7 (0x07)
    Program_map_PID: 262 (0x0106)

    Program_number: 43483 (0xa9db)
    reserved: 7 (0x07)
    Program_map_PID: 263 (0x0107)

    Program_number: 43484 (0xa9dc)
    reserved: 7 (0x07)
    Program_map_PID: 264 (0x0108)

    Program_number: 43485 (0xa9dd)
    reserved: 7 (0x07)
    Program_map_PID: 265 (0x0109)

    Program_number: 43486 (0xa9de)
    reserved: 7 (0x07)
    Program_map_PID: 266 (0x010a)

    Program_number: 43487 (0xa9df)
    reserved: 7 (0x07)
    Program_map_PID: 267 (0x010b)

    Program_number: 43488 (0xa9e0)
    reserved: 7 (0x07)
    Program_map_PID: 268 (0x010c)

    Program_number: 43489 (0xa9e1)
    reserved: 7 (0x07)
    Program_map_PID: 269 (0x010d)

CRC: 2266333291 (0x8715806b)
==========================================================

Is 'Program_map_PID' the value to be used to dump a raw TS?

[Pr2]

Google is your friend:

 

http://dvbsnoop.sour...xamplelist.html

 

So if you want the PMT from Program_map_PID: 258 (0x0102):

 

dvbsnoop -n 1 -nph 0x0102

[MeanMachine]

Thanks Pr2!

 

I'm learning the intricacies of DVB and MPEG-TS at the same time as well, so my understanding is improving as I experiment more with dvbsnoop. Currently trying to figure out the following:

1. Does one 'Program_map_PID' value correspond to one service (TV channel)?
2. How can PAT/PMT information be used to record/dump raw TS of a particular PID?
3. In what respect will this raw TS be different from the one recorded by OpenPLi by pressing the record button on remote control?
4. Will this raw TS be different from the ones which are supported by "cheap USB sticks" as mentioned by athoik in post #2?

Any help is appreciated!

[Erik Slagter]

You're some DVB basics here.

 

Every transport stream (which generaly corresponds to one transponder) carries one PAT (program association table), which is at a fixed PID. The PAT lists all of the "programs" (services) carried in the transport stream, it mentions the pid of the PMT (program map table) for each service. When you decode the PMT of each service, you will the PID's of it's elementary streams (audio/video/txt/pcr/etc) and some additional metadata. With these two you should be able to build a list of all used PID's in the transport stream. And then see how many you can have applied to the demuxer!

 

Regarding #3: a regular recording consists exactly of the complete transport stream received from the transponder, but only packets with PID's belonging to one (or two, or three...) services are actually in the file. That's the role of the demuxer. It actually doesn't only demux, but also filters PID (hence the "pid filters").

Edited by Erik Slagter, 17 May 2019 - 15:48.

[MeanMachine]

Thanks Erik for the detailed explanation. I was away for a few weeks hence a late reply.

 

For anyone who stumbles upon this thread later on: I needed to use "cheap USB sticks" to dump the required data. I'm still not sure whether it is a limitation of the drivers provided by Formuler for F4 turbo or something missing in OpenPLi/Enigma2 implementation.