Fun with DTV Transport Streams

[edDV]

I'm repeating a reply I made to zzyzzx in "Who cares if Analog TV goes dark?" here where it belongs for further discussion as a new topic.

More importantly, when will I be able to buy a NTSC DTV PCI card that does hardware MPG2 capture?

They all get you a MPeg2 TS stream captured to a file. The ATSC TS stream is a ~19 Mb/s multiplex of HDTV and/or SDTV subchannels plus other data.

Demultiplex software like HDTVtoMPEG2 will allow you to extract individual SDTV subchannels with associated audio and convert them to 704x480 MPeg2 suitable for DVD authoring. HDTV subchannels can also be extracted into 1080i or 720p MPeg2 files. These need to be downconverted to 480i/480p DVD spec by a software program like Sony Vegas. Downconversion is very time consuming in software and it would be great to get some hardware assist.

Individual SDTV streams are ~3-5 Mb/s
Individual HDTV streams are ~15-19 Mb/s

Some cable boxes in some communities provide TS streams for the channel being watched over an IEEE-1394 connector. If these are provided, the local DTV channels are usually unencrypted. Cable channels may or may not be encrypted. It all depends on what your local cable company is doing.

I've looked at several systems and this is what I've observed coming out of cable box IEEE-1394 connectors. The TS is formatted for D-VHS.

Analog channels may be locally (in the box) converted to 720x480i 8-8.5Mb/s streams where available. Quality varies by box model.

Cable MPeg digital channels output at ~ 528x480 at 1.8 to 15 Mb/s
HDTV locals output at various 720p or 1080i at 20 to 25 Mb/s
HDTV cable channels output mostly at 1080i 20-25Mb/s. ESPN-HD is the exception at 720p 25Mb/s.

Is this what others are seeing?

[Soopafresh]

I can verify your findings with OTA HDTV broadcasts in the US. BTW, every broadcast I have captured uses PID(s) 11,14 OR 31,34 for the main show. Downresing to 480p IS a long process (10fps on my 2.4 P4). I use AviSynth and HC for re-encoding.

[Nelson37]

Info I have seen over on AVSforum indicated that you could get a 3rd party box with firewire output even if your provider does not offer one. My sat company confirms that using a 3rd party decoder box is fine with them, obviously as long as you conform to usage limitations.

Had not seen that some 1394 output is encrypted, this would make it kinda useless. It was indicated that the DVHS recording could not be re-recorded due to some Macrovision-like inclusion in the video. Recording to the PC using DVHS emulation software eliminated this problem.

On the downsizing, my current thinking would be to encode as full HD resolution XVID, for use in a player supporting this. These seem to be getting more common and less expensive. Any thought on this as opposed to resizing for standard DVD?

There was also a company whose name I forget, AB 100 or something similar, which offered some kind of 1394 conversion box. It was firewire in and out, something over $100.00 and I was unclear what its exact purpose was. There was some mention of this on AVSforum, but no definite explanation.

I was under the impression that DVHS was the only allowed/approved technology to record true HD, apparently because it could be protected in some way? Is this correct, likely to be changed soon, ultimately what if anything will be the "authorized" way to record HD feed?

[edDV]

Had not seen that some 1394 output is encrypted, this would make it kinda useless. It was indicated that the DVHS recording could not be re-recorded due to some Macrovision-like inclusion in the video. Recording to the PC using DVHS emulation software eliminated this problem.

I've only heard this was the case. In April the FCC specifically prohibited cable companies from encrypting local rebroadcasts on this port although the local stations are free to encrypt their own signals and the cable companies can encrypt their own channels. Various technologies can be used such as DTCP to encrypt IEEE-1394.

On the downsizing, my current thinking would be to encode as full HD resolution XVID, for use in a player supporting this. These seem to be getting more common and less expensive. Any thought on this as opposed to resizing for standard DVD?

I just save the ts file to HDD and edited clips to DVDR (@ 30min per side) for now. HDTVtoMPeg2 quickly and easily chops a ts file for simple editing.

It is my understanding that HD tuner cards and upper range NVidia/ATI display cards include some form of HD scaling hardware but I haven't seen software drawing on these capabilities for 1080i to 480i or 720p to 480p conversion.

[leebo]

Ed, what hardware are you using to capture HD?
Also, are you capturing OTA and/or cable/sat?

Do you have any particular recommendations for an HD capture card for OTA?

[edDV]

Ed, what hardware are you using to capture HD?
Also, are you capturing OTA and/or cable/sat?

Do you have any particular recommendations for an HD capture card for OTA?

I'm using IEEE-1394 connection to Motorola DTC-6200 (or 6412) HD cable box.

Sometime in the last month Comcast blocked TS streams from normal SD "digital" cable and HD cable channels. All I get now are local SD/HDTV channel TS streams (20 to 25 Mb/s) and inbox analog channel to 720x480 8.5Mb/s TS conversions. Your mileage will vary locally.

Due to local topographic conditions, I can't get OTA HDTV here. I've only had limited experience with the ATI HD Wonder and a Fusion HDTV cards. Both worked OK with strong signals in the SF Bay area.

[leebo]

Hmm.. I remember when they were building Sutro I thought they would never need anything higher. Guess I was wrong.

I'm in LA now.

I've been doing a lot of reading over at AVS. Hope to eventually come up with a computer based HD PVR.

[edDV]

Hmm.. I remember when they were building Sutro I thought they would never need anything higher. Guess I was wrong.

I'm in LA now.

I've been doing a lot of reading over at AVS. Hope to eventually come up with a computer based HD PVR.

I'm up in the Sierra foothills. People on the other side of the ridge are getting HDTV off Sutro fine @ >150 miles but at 3,000 feet altitude. People in the Sacramento Valley have trouble with Sutro during ground fog conditions (most of the fall and winter).

[leebo]

Ah. You're in "North" Northern CA.!