Join Date: Jun 2001
Location: Mountain Lakes, NJ
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I'm glad the D-VHS demo taps are still playing, we encoded the content for Panasonic. The comment about them not playing at all on other machines reinforces my suspicion that while the RF tracking may be compatible between machines, the method of encapsulating the transport stream may not be standardized.
The equipment needed to create the tapes from either a test generator, HD-D5 or HDcam tape is formidable. Don't expect it to be affordable to a hobbyist for a long time.
Here's how we do it.
First, we receive content on an HD tape format, sometimes with a second tape (DA-98) with surround audio. Frequently the tapes need minor editing to add lead in/out black. Recently we have seen an expanding use of Dolby "E" data which can put 8 channels of audio on two channels of an unmodified HD-D5 vtr.
One of our broadcast ATSC encoders is set to the desired stream rate. If we are creating a high quality file, the rate could be set as high as 80 Mbps and 4:2:2 sampling. For D-VHS and Sencore 995/996 players, we set the encoders to ATSC rates and 4:2:0 sampling. The AC-3 encoder is set to 384k which is not mandatory but is what most stations have selected as a normal operating value. This rate is the minimum that will support 3/2L (5.1) encoding. We can go down to 192K for 2/0 and up as high as 448k.
Once this is set, we "time" the program and create a null file in a high performance NT workstation using a variety of GUI based apps with DVB interfaces.
We then use a broadcast editing system to cue / run the playback vtr, start the workstation and record the stream from the encoder into the null file. Once this is done, we QC the file through an analyser to look for all types of errors.
Lastly, for D-VHS, we play the file through a broadcast 8VSB exciter (we use Harris and Zenith products), into the DST50 or 51 and thence into the D-VHS in record mode.
Some variations that we add include closed captions, second audio programs, SD/HD multiplexes and PSIP since the new Hughes designed box (Mits, Toshiba, Philips, Hughes) do not tune reliably without these tables.
It's very expensive! To do this reliably, you need multiples of all the listed equipment. I didn't even mention the "Glue"; sync generators, GPS clocks, switching, patching etc.
Pete Putman has asked me for a D-VHS test tape. If we can get a consensus on the types of signals that would be useful to everyone, I'll make a master D-VHS tape. I just don't want to do this creation task a hundred times.
Since gridleak has all the decks maybe we can volunteer him to make dubs.
The comments about the channel number display are related to the presence or absence of PSIP. It is NOT required by FCC rules at present for broadcast. The Dish 5000 remod does not create PSIP. (That process costs about $30,000.00) In fact the HD streams off Echostar III are DVB streams. In the case of WCBS-DT, the Echostar stream only includes the elementary audio and video pids.