DTV Tuner questions

[marshallarts]

I have an old Dell Studio 1745 laptop, which has a built-in digital TV tuner. It was originally running under Windows 7, but when I upgraded to Windows 10 there was no longer an available driver for the TV tuner. The laptop is not used a lot these days, so I thought I would try running it with Mint 21. So far I am very impressed. It got me wondering if it might be possible to get the TV tuner going again, under Linux. Yes I concede that this is a very old computer (maybe over 10 years), but it is built like a tank and has a beautiful big screen, so I am not about to throw it out. I've been working with computers for over 50 years, but not a lot with Linux. Anyway, the details so far...

The documentation that came with the laptop suggests that the tuner is an AverMedia TVT17. I cannot find any reference to that product code on the AverMedia website, so it may be a Dell code.
I have used the lspci command, and it tells me that I have a multimedia device which is a Philips SAA7231 (rev ca). A bit of searching has found some mentions of that, and it seems that it is indeed a TV tuner. But I haven't (yet) come across any info on drivers, or how to configure it in LM. Or if that is even possible.

That's about as far as I have got so far. If anyone knows if/how this hardware can be used in LM, it would be good to be pointed towards some useful info. Thanks.

EDIT: Further searching has revealed that it seems very unlikely that this device can be made to work under Linux, at least partly because of non-cooperation from the original chipset manufacturer (apparently someone called NXP, not Philips). So this enquiry is probably a dead end. No big deal, I can still enjoy LM on this computer. But if anyone knows different, I'd love to know about it.

[freshminted]

Have you checked the linuxtv site? https://linuxtv.org/

May be some help there.

[marshallarts]

Thanks, yes I did find that site and have had a look. I didn't find it all that easy to navigate actually. There is mention of some other SAA7xxx chipsets, but I could not see anything about the SAA7231.

[marshallarts]

I am changing direction with this. Forget the inbuilt TV tuner!

I also have a USB TV tuner, a Kaiser Baas which is quite a few years old but I am fairly certain IS supported in the LM kernel. lsusb identifies it as follows:

Bus 002 Device 004: ID 1164:2edc YUAN High-Tech Development Co., Ltd STK7700D

And dmesg shows it being detected and initialised:

[ 121.488208] dvb-usb: found a 'Yuan PD378S' in cold state, will try to load a firmware
[ 121.488369] dvb-usb: downloading firmware from file 'dvb-usb-dib0700-1.20.fw'
[ 122.221453] dvb-usb: found a 'Yuan PD378S' in warm state.
[ 122.221834] dvb-usb: will pass the complete MPEG2 transport stream to the software demuxer.
[ 122.222007] dvbdev: DVB: registering new adapter (Yuan PD378S)
[ 122.223336] dvbdev: dvb_create_media_entity: media entity 'dvb-demux' registered.
[ 122.466856] dvbdev: dvb_create_media_entity: media entity 'DiBcom 7000PC' registered.
[ 122.709572] dvb-usb: schedule remote query interval to 50 msecs.
[ 122.709576] dvb-usb: Yuan PD378S successfully initialized and connected.

However I have tried using it with VLC (which works fine with this device on Windows 10) but I get no audio or video. I open a capture device, select TV - Digital in the top drop-down, /dev/dvb/adapter0 as the device and it has already selected DVB-T as the Delivery System. I enter a frequency which has worked on Windows.
I have also tried Kaffeine with similar results, but Kaffeine usually crashes with a segmentation fault after selecting a channel. I feel like this should work, so I am probably missing something fairly simple but I don't know where I should be looking. Any suggestions welcome.

[freshminted]

In vlc I also have to select the bandwidth (7MHz here in Australia). Leaving it on automatic just leaves it waiting forever.

[marshallarts]

Thanks, that did change the behaviour - slightly. I'm in Australia too (WA), so selected Bandwidth = 7MHz. (This doesn't seem to be necessary on Windows.) There was a very brief snatch of audio, but no picture, then VLC crashed with the same segmentation fault I have seen in Kaffeine. That hasn't happened before with VLC, so maybe it is actually getting a bit further than it was before, and is now encountering the same problem that Kaffeine has.

[freshminted]

I've not had the problems you describe, with any of the usb tv sticks I use (pinnacle, kaiser-baas, others). But you must have a good antenna signal going into the tv stick, or the video and audio will pixelate badly and maybe even lock up and core-dump out of the program.

Also, these command line tools https://linuxtv.org/wiki/index.php/DVBv5_Tools have proved useful for getting more info about tv signal quality etc.

[marshallarts]

Thanks for the link, will investigate that but I'm sure the signal level is fine. I always connect to a wall point that goes to the rooftop antenna, never had any problem on Win10.

[marshallarts]

I installed the tools mentioned above, and tried the dvbv5-scan utility. I was slightly surprised to see that it often described the signal quality as "Poor". Not always, but often. This was on both antenna outlets I have in my house. So maybe that is an issue. I keep coming back to the fact that this same tuner works fine on Windows10 with VLC and also with a TV viewer program I have found. But I accept that digital TV is all about software, and it's possible that the Linux software has different parameters for signal quality than the Windows platform does.

So I'm not sure where to go with this. The antenna on my roof is not all that old, because the original one basically fell down a few years back. I do have a splitter in the roof space so that cables can run to the two wall outlets, so maybe the connections on that are not so good. A few things to think about. It would still be much nicer if VLC and Kaffeine didn't crash though - by all means indicate if the signal quality is not good enough, but don't crash.

[freshminted]

There is the perverse possibility that your signal is too strong! I've run into this occasionally. You can fix it with an attenuator on the antenna feed.

[marshallarts]

Well, never would have thought of that! Is it possible to quantify how strong is "too strong"? The scan tool reports signal levels like -43dBm, plus or minus a few. I also have a signal strength meter which I use in a caravan for aiming the antenna, so I tried that. It has a row of 4 LEDs which it lights progressively as the signal gets stronger. I plugged the antenna cable into it, at the end that goes into the TV tuner. On one of my wall outlets I see 2 of the LEDs lit, and on the other (where our TV is plugged in) only 1. On the face of it, that seems to me to be on the weak end rather than the strong. But I don't have technical knowledge in the RF area.

[freshminted]

Yeah, sounds like signal too weak is more likely. My antenna occasionally overwhelms one of my usb tuners (on windows) with too strong a signal causing pixellation and bad recordings, especially during summer.

I have an Avermedia usb stick that looks like it never made it into the linux kernel. Can read old instructions about fixing that here: http://faqload.com/faqs/technology/linu ... t-11-katya, but I'm not going to fiddle with compiling kernels - the display on that particular computer is a TV, so if I want to watch tv on it, I use it as a TV! Your card is probably in the same boat, but have you checked https://linuxtv.org/wiki/index.php/DVB-T_devices?

[marshallarts]

Yes, according to linuxtv.org the tuner is definitely supported in the kernel, since 2.6.30. A bit surprising given its age, but that's what it says. I can see in the dmesg log that it is being detected and (apparently) initialised. And the fact that the scan tool can see channels and sub-channels means it is definitely working at some level. It's certainly no big deal if I can't get audio and video out of it, I just like to know what is going on!

[freshminted]

Can you record a .ts file using dvbv5-zap (part of the dvb-tools you've downloaded)?

Go through the steps to create a channel list in viewtopic.php?t=302540 to use dvbv5-zap, don't worry about using the at stuff to create a schedule.

[marshallarts]

Many thanks for that, very instructive. I was indeed able to do all the necessary scans etc, and record some video from a chosen channel. So I don't think there is any doubt that the data is being received and decoded as it should be. The resulting .ts file can be played directly in the Mpv media player, and also in Celluloid. It definitely did NOT play in VLC - it sent the whole computer into a tailspin and required a restart! So I grabbed ffmpeg and made a couple of attempts at converting the .ts to a .mp4. Mpv and Celluloid can play the resulting mp4 happily, but again, VLC would not - maybe I need to study the many options available on ffmpeg. It's worth mentioning that ffmpeg did show several error messages during the conversion. So I'm coming to the conclusion that VLC on Linux might just be a bit buggy - it's version 3.0.16 which is not very old, but not the very latest. I will investigate whether Mpv and/or Celluloid can open the tuner device directly, or if there are any other alternatives to VLC - I'm sure there are heaps!

Thanks again, this is a fascinating journey!