"No Descrambler" on channels with no CCI encryption.

John Nevill · 2012-10-29T15:47:32+00:00

I have an hdhomerun prime with a Comcast m-card and HD subscription. I have compiled tvheadend 3.2 from source on my Ubuntu 12.04 x64 machine and I am using...

Villy Thomsen

Hi Jim,

> I've been working on an alternate approach to doing the PID <-> Virtual Channel mapping in dvbhdhomerun. Basically, in HdhomerunTuner::StartStreaming, I call hdhomerun_device_get_tuner_streaminfo to get virtual channel information for the currently tuned frequency. For each program found, I select it using hdhomerun_device_set_tuner_program, then call hdhomerun_device_get_tuner_filter to get the PID filter that has been applied as a result of the set_tuner_program call. If it matches the PID passed to the StartStreaming call, then I have the correct program. If I can't find a program that matched the PID, I fall back to the original logic of setting the PID filter directly.
>

I did not know about the hdhomerun_device_get_tuner_streaminfo(), sounds like that'll make everything much easier.

> I've got this implemented, but I still have to test it. I'd be interested in any comments or suggestions you might have. In particular, do you see any reason why this can't work or is a really bad idea? If not that, then I'd appreciate anything you can tell me about how to test this.
>

Hmmm, to keep it simple just do the hdhomerun_device_get_tuner_streaminfo() + hdhomerun_device_set_tuner_program() for starters. get_tuner_filter() and checking wait with that.

One thing to keep in mind, is that StartStreaming() will be called a bunch of times when a program is tuned. One for each video/audio/teletext PID. That is just the way it is done in the linux kernel. But I don't see any harm in calling streaminfo() + set_tuner_program() each time it is hit.

Also keep in mind that set_tuner_program() only seems to work for one program per mux, so don't schedule two program on the same mux for starters - that'll screw things up. Otherwise, go go go! :-)

Villy Thomsen

Villy Thomsen wrote:
> Hi Jim,
>
> > I've been working on an alternate approach to doing the PID <-> Virtual Channel mapping in dvbhdhomerun. Basically, in HdhomerunTuner::StartStreaming, I call hdhomerun_device_get_tuner_streaminfo to get virtual channel information for the currently tuned frequency. For each program found, I select it using hdhomerun_device_set_tuner_program, then call hdhomerun_device_get_tuner_filter to get the PID filter that has been applied as a result of the set_tuner_program call. If it matches the PID passed to the StartStreaming call, then I have the correct program. If I can't find a program that matched the PID, I fall back to the original logic of setting the PID filter directly.
> >
> I did not know about the hdhomerun_device_get_tuner_streaminfo(), sounds like that'll make everything much easier.
>

Hmmm, no on closer inspection that doesn't look like it will work. get_tuner_streaminfo() returns all programs on the mux no matter what you have set for PID filtering (I think), but do try it anyway if I am wrong.

In any case I think you are on to something, there may be something else in the API that can gives us what we need. I don't have much time tonight (I'm in denmark btw, so there is some time difference) so do keep looking. ;)

Villy Thomsen

Villy Thomsen wrote:
> Villy Thomsen wrote:
> > Hi Jim,
> >
> > > I've been working on an alternate approach to doing the PID <-> Virtual Channel mapping in dvbhdhomerun. Basically, in HdhomerunTuner::StartStreaming, I call hdhomerun_device_get_tuner_streaminfo to get virtual channel information for the currently tuned frequency. For each program found, I select it using hdhomerun_device_set_tuner_program, then call hdhomerun_device_get_tuner_filter to get the PID filter that has been applied as a result of the set_tuner_program call. If it matches the PID passed to the StartStreaming call, then I have the correct program. If I can't find a program that matched the PID, I fall back to the original logic of setting the PID filter directly.
> > >
> > I did not know about the hdhomerun_device_get_tuner_streaminfo(), sounds like that'll make everything much easier.
> >
> Hmmm, no on closer inspection that doesn't look like it will work. get_tuner_streaminfo() returns all programs on the mux no matter what you have set for PID filtering (I think), but do try it anyway if I am wrong.
>

> In any case I think you are on to something, there may be something else in the API that can gives us what we need. I don't have much time tonight (I'm in denmark btw, so there is some time difference) so do keep looking. ;)

Seems like simply:

hdhomerun_device_get_tuner_program()

Is exactly what we need. So instead of get_tuner_streaminfo() just use that one. That gives exactly what program is tuned.

Jim Ancona

Villy Thomsen wrote:

> Hmmm, no on closer inspection that doesn't look like it will work. get_tuner_streaminfo() returns all programs on the mux no matter what you have set for PID filtering (I think), but do try it anyway if I am wrong.

Right, that's why I took sort of a backwards/indirect approach. I iterate through each program returned by get_tuner_streaminfo(), tune to it using set_tuner_program(), then call get_tuner_filter() to see if the PID matches, which means I've found the right one. That's kind of strange and possibly inefficient, but it's the only way I could figure out so far.

Villy Thomsen

Hi Jim,

> > Hmmm, no on closer inspection that doesn't look like it will work. get_tuner_streaminfo() returns all programs on the mux no matter what you have set for PID filtering (I think), but do try it anyway if I am wrong.
>

> Right, that's why I took sort of a backwards/indirect approach. I iterate through each program returned by get_tuner_streaminfo(), tune to it using set_tuner_program(), then call get_tuner_filter() to see if the PID matches, which means I've found the right one. That's kind of strange and possibly inefficient, but it's the only way I could figure out so far.

You may have missed a posting there - but simply use this instead ofgettuner_streaminfo():

hdhomerun_device_get_tuner_program()

It returns the program that is tuned now, so you can use that directly in set_tuner_program()

Jim Ancona

Villy Thomsen wrote:
> Seems like simply:
>
> hdhomerun_device_get_tuner_program()
>

> Is exactly what we need. So instead of get_tuner_streaminfo() just use that one. That gives exactly what program is tuned.

Perhaps I'm misunderstanding something (wouldn't be the first time). The way I understand the problem with the HDHR Prime is that just setting a PID filter doesn't cause the box to do the additional CableCARD magic to decrypt the stream. In order to do that you have to call set_tuner_program() instead of just . But that requires a program number, when all we have is a PID. Are you suggesting setting the PID filter, then calling get_tuner_program() to get the program number? I can try that, but I'd be surprised if it worked. Am I missing your point?

Jim Ancona

Ok here is the w_scan output (both stderr and stdout) and the output of

hdhomerun_config 131605CE scan 0 scan0.txt

so you can compare that.

Villy Thomsen

Jim Ancona wrote:
> Villy Thomsen wrote:
> > Seems like simply:
> >
> > hdhomerun_device_get_tuner_program()
> >
> > Is exactly what we need. So instead of get_tuner_streaminfo() just use that one. That gives exactly what program is tuned.
>

> Perhaps I'm misunderstanding something (wouldn't be the first time). The way I understand the problem with the HDHR Prime is that just setting a PID filter doesn't cause the box to do the additional CableCARD magic to decrypt the stream. In order to do that you have to call set_tuner_program() instead of just . But that requires a program number, when all we have is a PID. Are you suggesting setting the PID filter, then calling get_tuner_program() to get the program number? I can try that, but I'd be surprised if it worked. Am I missing your point?

Hi Jim,

That was my thought exactly. It's worth a try at least. Long shot of course, since if it actually knew which program it was tuned to via the PID's it would probably have decoded it....

Villy Thomsen

Jim Ancona wrote:
> Ok here is the w_scan output (both stderr and stdout) and the output of

hdhomerun_config 131605CE scan 0 scan0.txt

so you can compare that.

Thanx. Well, it does look like it contains what we need for a mapping - I'll see if I can teach userhdhomerun to eat the output from w_scan.

I should probably make it flexible so that you can use it as a "cache" if your method works. E.g. when you tune to a frequency the first time, store the PID's + program you get from it to the cache, so that next time you tune to that frequency you can just look it up in the cache instead of having to go through all the programs again.

Maybe your method could be used as a startup thing? Hmmm. Need more thinking. ;)

Jim Ancona

I tried adding the get_tuner_program() call immediately after the set_tuner_filer() in StartStreaming() (without calling set_tuner_program()). Unfortunately it always returns "0". :-(

As I'm doing more testing there's something I don't understand about the way TVheadend uses the DVB interfaces. I'm working in the StartStreaming() method and when I make a request to record or stream a channel I see multiple calls to StartStreaming for multiple PIDs. The logs look like this:

FE_SET_FRONTEND, freq: 495000000 sym qual: 64 START FEED: Pid = 0 In StartStreaming: _pid: 0 PidFilter: 0x0 hdhomerun_device_set_tuner_filter: 0x0 hdhomerun_device_stream_start: 1 FE_READ_STATUS Open data device: /dev/hdhomerun_data2 Open data device: /dev/hdhomerun_data2 sym qual: 64 START FEED: Pid = 1 In StartStreaming: _pid: 1 PidFilter: 0x0 0x1 hdhomerun_device_set_tuner_filter: 0x0 0x1 START FEED: Pid = 1ffb In StartStreaming: _pid: 1ffb PidFilter: 0x0 0x1 0x1FFB hdhomerun_device_set_tuner_filter: 0x0 0x1 0x1FFB START FEED: Pid = 1a01 In StartStreaming: _pid: 1a01 PidFilter: 0x0 0x1 0x1FFB 0x1A01 hdhomerun_device_set_tuner_filter: 0x0 0x1 0x1FFB 0x1A01 START FEED: Pid = 1a03 In StartStreaming: _pid: 1a03 PidFilter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 hdhomerun_device_set_tuner_filter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 START FEED: Pid = 1a0d In StartStreaming: _pid: 1a0d PidFilter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D hdhomerun_device_set_tuner_filter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D START FEED: Pid = 1a00 In StartStreaming: _pid: 1a00 PidFilter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D 0x1A00 hdhomerun_device_set_tuner_filter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D 0x1A00 START FEED: Pid = 17a0 In StartStreaming: _pid: 17a0 PidFilter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D 0x1A00 0x17A0 hdhomerun_device_set_tuner_filter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D 0x1A00 0x17A0 START FEED: Pid = 1a10 In StartStreaming: _pid: 1a10 PidFilter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D 0x1A00 0x17A0 0x1A10 hdhomerun_device_set_tuner_filter: 0x0 0x1 0x1FFB 0x1A01 0x1A03 0x1A0D 0x1A00 0x17A0 0x1A10 FE_READ_STATUS

Note that the above is all to stream/record a single program. Do you know what TVHeadend is trying to do?

John Nevill

So... given my Comcast/tsid issue I had the great thought that maybe I could spoof the tsid for each mux so tvheadend doesn't balk at all the 0x00's. I've seen a few other folks out there dump a hdhomerun_config scan from comcast and it looks like I'm not the only one that suffers from this issue.

Villy, any suggestions you might have for hacking on userhdhomerun to pull off a tsid spoof. From what I've seen the TSID needs to be static for each mux, and it looks like a 16 bit positive integer, so given that the range of potential frequencies is fixed, I figured I could just divide each frequency by a sufficiently large number and pass that back up so tvheadend is none the wiser.

Jim, if there is anything I can help with or test on the virtual channel front, let me know. I haven't written in C++ before, but I do code in a handful of other languages so I can stumble around without breaking things too badly.

You guys rock.

Jim Ancona

I have a patch that works sometimes. I'm trying to understand why it doesn't work all the time. One possible explanation is that dvbhdhomerun plus patch is working fine, but there are other problems with my TVHeadend setup.I'm going to try to do some more troubleshooting on that front this evening.

Jim Ancona

I still haven't been able to figure out what distinguishes channels that work from those that don't with my patch. If anyone wants to test it, I've uploaded it to the dvbhdhomerun issue tracker here: https://sourceforge.net/apps/trac/dvbhdhomerun/ticket/12

I'd appreciate any feedback. Thanks!

Jim Ancona

My patch now works reliably and tvheadend now can record and stream reliably from my HDHR Prime. I've attached "the patch" to "the issue" on the dvbhdhomerun tracker. If you can build dvbhdhomerun, please give it a try and let me know how it works.

great front7

I've been following this thread for a while because I have the same set-up: Comcast cable card w/ a Prime that I have never been able to get TVHeadend to work with, so really excited to see some progress happening! Any chance someone would be willing to share some pointers on how to apply Jim's patch for a non-developer?

Jim Ancona

What it takes to build from source varies quite a bit depending what platform you're deploying on, and dvbhdhomerun/tvheadend seem to be the kinds of packages that people use on a variety of different distros and architectures. If you haven't built from source before, your best bet may be to wait for Villy to incorporate my code into a release. Otherwise, you can try following the build instructions on the wiki: https://sourceforge.net/apps/trac/dvbhdhomerun/wiki/Building, but those may not work for you if you're not using vanilla Debian/Ubuntu/Fedora (e.g. I had to tweak things a bit and do some research to get them to work on my Raspberry Pi).

Villy Thomsen

Hi Jim,

> My patch now works reliably and tvheadend now can record and stream reliably from my HDHR Prime. I've attached "the patch" to "the issue" on the dvbhdhomerun tracker. If you can build dvbhdhomerun, please give it a try and let me know how it works.

Looks good, I'll play around with it a bit. I do have some PID<->Program cache going on here (for my attempt to parse the output from w_scan), I'll see if I can integrate that with your code. Probable C++-ify it a bit on the way too. ;-)

I'll make a branch in CVS on the sourceforge repository with your patch + my cache stuff so we can use that as a merging point, that will maybe happen tonight.

FYI, I will be travelling (to the US actually) next week, so will likely not be that much available.

Jim Ancona

Villy Thomsen wrote:

> I'll make a branch in CVS on the sourceforge repository with your patch + my cache stuff so we can use that as a merging point, that will maybe happen tonight.

I'll check it out. Thanks!

> FYI, I will be travelling (to the US actually) next week, so will likely not be that much available.

Have a good trip! Where are you going to be?

Villy Thomsen

> > FYI, I will be travelling (to the US actually) next week, so will likely not be that much available.
>
> Have a good trip! Where are you going to be?
>
New London, Connecticut - via Boston.

Jeremy Keeney

If you guys make a .12 by tonight with those patches, I will be the happiest person alive!!

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