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After some talk at work last week, I figured I should put the coax jack in my den to some good use, and started looking around for some HDTV tuner cards. I'll whet your appetite with some (NBC 1080i) screenshots:
I realized I would need (at the bare minimum) an ATSC card with a QAM tuner to view the channels provided by my Time Warner Cable digital cable service here in Charlotte. Initially, the use of the term DVB in many LinuxTV articles confused me, but I soon found out that the Linux DVB subsystem works with ATSC cards, too. It's somewhat of a misnomer, since DVB used on its own refers to the digital TV standard in Europe.
After consulting the list of supported cards, I picked up (impulse buy, of course) a DViCO FusionHDTV5 RT Gold PCI card, which seemed to sport a complete featureset. It uses the Conexant cx2388x chipset, which is supported on the somewhat jacked-up 2.6.22-gentoo-r5 (x86_64) kernel I've been running as of late.
I was lazy, and modularized the kitchen and sink. CONFIG_KITCHEN and CONFIG_SINK are required, and will increase your kernel size +32MiB.
No, really, in Multimedia devices, I modularized everything under Video capture adapters, and DVB/ATSC adapters. Thankfully, udev autoloaded it all for me upon bootup, so I didn't really have to do a thing. Here's a short list of relevant modules:
Module Size Used by btcx_risc 4808 4 budget 12868 0 budget_av 20160 0 budget_ci 18116 0 budget_core 10180 3 cx8800 32044 0 cx8802 16452 1 cx88_alsa 12808 0 cx88_dvb 15428 4 cx88_vp3054_i2c 4352 1 cx88xx 64484 4 dvb_core 76144 7 dvb_pll 14404 3 dvb_ttpci 94848 0 ir_common 32260 2 lgdt330x 9092 1 saa7146 16264 6 saa7146_vv 45312 2 ttpci_eeprom 2944 2 tuner 61480 0 tveeprom 17232 1 v4l1_compat 11972 2 v4l2_common 18304 6 ves1820 6596 0 video_buf 21828 7 video_buf_dvb 5764 1 videodev 26304 3
The ir_common is for the IR port, that I failed to hook up (lack of interest), on the card. And, that's about it…
From the start, it looked like dvbscan, azap, Kaffeine, and MPlayer were going to be my friends. In fact, MPlayer is already my friend, since I ditched Xine awhile back.
I emerged the following:
(I'd link to packages.gentoo.org, but that site's been dead for several weeks, now)
After reading some documentation, I realized I would need to create a channels.conf file, which is read by a number of DVB applications, and is composed of the (colon-delimited) channel name, frequency (in Hz), modulation type (QAM_256, 8VSB), video PID, audio PID, and program PID. The easiest way of creating this channels.conf is to run scan or dvbscan (former is for ATSC, but the latter works, too) by giving it an initial tuning data file. I saw a couple candidates (us-NY-TWC-NYC, us-Cable-Standard-center-frequencies-QAM256, us-ATSC-center-frequencies-8VSB) but eventually just catted them all together and launched dvbscan with the verbose flag.
This is about where I started pulling my hair out. Ok, that's an exaggeration.
dvbscan wasn't finding ANY channels. I was just seeing stuff like this for every frequency:
>>> tune to: 75000000:QAM_256 (tuning failed) >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 >>> tuning status == 0x02 WARNING: >>> tuning failed!!!
I unplugged the coax cable, and the tuning status changed to 0x00 for every frequency. Sounded like I had a signal, but maybe it was just too weak? I brought my old 20" clunker TV into the room, and plugged it in. Seemed fine, but was a bad test since it's analog. I checked out the cable splitters in the laundry room "telecom box" and removed the one feeding the bedrooms, plugging the den port directly into the feed coming from the junction box on the other side of the building. Voila, tuning success! Purchasing a 2GHz splitter did little good, as too much of the signal was degraded, so I eventually just closed it up and kept the two other bedrooms disconnected (who cares, they don't have TVs anyway).
Back to the channels.conf. The us-Cable-Standard-center-frequencies-QAM256 seemed to produce the best results, so I stuck its dvbscan output in channels.conf, and renamed some of the channels. The weird thing is, the initial channel names were [xxxx], where xxxx is some hex ID value, but they were repeated on different frequencies. However, if I changed the channel names appropriately, and tuned both frequencies, I got the same program content. I'm no cable whiz, (skipped cable 101, due to scheduling conflicts) but I assume it's being broadcasted this way for a reason.
Anyhow, here are some channels (channels.conf style) I was able to tune that are relevant to Time Warner Cable in Charlotte:
NBCHD:651000000:QAM_256:2045:2044:164 ABCHD:579000000:QAM_256:2033:2032:6 WCNC:651000000:QAM_256:2045:2044:164 FOX:579000000:QAM_256:0:0:8 CW:579000000:QAM_256:1632:1631:9 WTVI:585000000:QAM_256:141:143:2 WTVI2:585000000:QAM_256:147:148:3
The quickest way of tuning and viewing the MPEG stream is to first select the channel with azap -r [channel name], and then playing /dev/dvb/adapter0/dvr0 with mplayer. azap should show you something like this:
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0' tuning to 579000000 Hz video pid 0x0664, audio pid 0x0663 status 00 | signal 4b11 | snr 0a43 | ber 00000000 | unc 0000ffff | status 1f | signal d7a9 | snr 1d7c | ber 00000000 | unc 0000ffff | FE_HAS_LOCK status 1f | signal d6e6 | snr 1d61 | ber 00000000 | unc 00000000 | FE_HAS_LOCK
The FE_HAS_LOCK indicates that the card has locked the frequency and is getting a clear signal. If you don't see that, then either the signal is too faint, or something else is wrong.
MPlayer then will start streaming the TS packets from /dev/dvb/adapter0/dvr0 and decode them to the screen, excellent! You can also cat /dev/dvb/adapter0/dvr0 to a .ts file, and save the raw MPEG packet data to disk. Neat, huh?
I also tried Kaffeine, which took a little hacking to get working. Apparently the DVB support doesn't include ATSC scanning, so the $HOME/.kde/share/apps/kaffeine/channels.dvb must be converted from an existing channels.conf. Check out this thread. Downloading and building the atsc-converter utility worked fine. Kaffeine was then able to see a list of channels. Viewing them is just a click away.
I haven't discovered all the channels, yet.. this will take some time. I also need to mess with mencoder, and encode the TS data into something smaller. MythTV is also on my list of things to try.
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