The death of videotape; long time coming.

Say it ain't so! I read the news today, oh boy.....

Sony is to stop selling its range of ½-inch tape machines and camcorders in just over a year’s time. The manufacturer has targeted March 2016 as the date by which it will cease sales and distribution of its professional VTRs and camcorders, owing to what it described as “the global trend of migration towards file-based operation”.

VTs have been a constant feature of my 26 years in broadcast engineering - I spent three years in VT maintenance when I was in BBC TV News and all through my time in facilities in the nineties/early noughties and my last dozen years working for a reseller the most dense way of storing data (which is what video has been for twenty years) is on magnetic tape using a rotating head-drum. 

VTRs are mechanical and hence unreliable; you can't pull rust-on-sellotape (a crude description of videotape) over a rotating metal drum without things wearing out and when I started I estimate that at least a half of all broadcast engineering hours were spent fixing decks. I certainly enjoyed that mix of electronics and mechanics and when I left BBC TV news my supervisor in VT maintenance had this made for me - at the time he reckoned I had done more than a hundred head-drums.

So, here are a few memories about VT formats I have had to deal with. It was all analogue when I started with the D1 format just starting to make inroads. By the mid-90s DigitalBetacam had become the predominant format for most production and post-production and Sony continued their domination of tape formats with HDCam and HDCamSR in the late nineties/early noughties. Since then it's been disk-based (XDCam) and flash-based (SxS, P2 etc etc.) - I haven't done anything more than cleaning a tape path or head-drum in the last decade but I used to be a pretty good VT-fixer!

• 2" Quad; The original broadcast tape format which was on the wein when I joined the Beeb. At Lime Grove studios we did have a couple of Ampex VR 2000 machines. These beasts needed a compressed air feed to hold the tape on the transversely rotating drum. They weren't used for editing, just for archiving P as B recordings. I remember watching an episode of "Star Trek" (original!) being transmitted and marveling at home good composite pictures could look.
• 1" C-format; specifically the Ampex VPR-2B (which was the BBC's 1" of choice) was a bit more of a workhorse machine. Again, BetaSP and Umatic HiBand where more prevalent at BBC News when I was there but when I went out into the independent industry in 1993 1" was a lot more widely used, particularly the Sony BVH-series machines (the choice when I was at CTV in St John's Wood) and then the Ampex VPR3 when I got to Soho in 1994 mastering to an analogue format was already diminishing.
• BetacamSP; The BVW75P was the first piece of broadcast equipment I got to know to the component level. The summer after I joined the BBC they bought three hundred of them and I jumped on the overtime to do acceptance testing. Consequently I got to know the signal path and then in 1990 I got transferred to VTR maintenance and pretty much serviced the same machines I'd been taking delivery of two years before. They were the broadcast workhorse until the late nineties and I still see them. When I went to Nigeria the whole place was still running on them. Here are some photos of the insides.
• D1; I didn't get into Soho until the second generation of D1s had arrived - the DVR2000 series (the 1000 series had half a rack of processing for trick-speed playback). D1 was the first 8-bit uncompressed SD VTR format. All the high-end facilities in Soho made good money out of them - when you could hire a 3 machine D1 room for £650 an hour! Many a time I heard engineers dismiss DigiBeta for it being compressed but I've NEVER seen Digi compression artifacts but I have seen shallow ramp banding on D1 (8-bit vs 10-bit). D1 decks were very expensive (£100k) and cost an arm and a leg to maintain. However - being able to do more than half a dozen generations on and off tape gave rise to all those effects heavy pop videos in the early nineties.
• D2; Sony quickly realized that they'd need a composite digital machine for run of the mill TV production work (i.e. people who needed a drop-in replacement for 1") and so they bought the format off Ampex in some complex licensing deal that allowed Ampex to sell badged BVW75s. Ampex's VPR300 was a terrible machine; we had them at Oasis TV and you could often not get recordings made in the morning to playback on the same machine in the afternoon. After that the Sony DVR28 was an eye-opener. It could stripe tapes at high speed as well!
• D3; Like D2 a digital composite machine but like D5 a 1/2" tape path which meant a practical all-in-one camcorder was possible. The BBC embraced the AJD350 the year I left and according to a pal at Panasonic of the first 98 machines they never got more than sixty working simultaneously. They format got really good after v.2 software when stability, RF performance etc improved. The operational side of the machine was entirely unlike Sony with a very complicated screen surrounded by buttons. Panasonic had to replace heads - almost no usable serviceable parts inside...!
• D5; Channel Four were the only UK broadcaster to commit to D5 which was Panasonic's answer to D1 (but, a 1/2" format with 10-bit video, uncompressed - eventually there was an HD variant as well). You could tell the machine ran so close to the edge in terms of heat performance. We had two of them at Oasis and every morning I would pull out the long boards (below the tape transport) and re-seat all the chips - a day's worth of heat made all the socketed devices rise up. The machine shared mechanics with the AJD-350 D3 machine and with an option decoder board would replay D3 tapes. The tape-stock was the same in both cases and when I was at CTV we would send "D5" masters to Channel Four which were really D3 recordings with a D5 card in the tape sleeve! They never spotted it and it saved us hiring D5 machines (we owned D3). The rumor at the time was that C4 had been given the initial set of machines free to establish the format which was (even then) viewed as entirely unsuitable for a broadcaster. I never id much maintenance on them save cleaning etc. You had to send them back to Panasonic for heads etc.
• DigiBeta; Whereas the first gen digital VTs (uncompressed, either 230mBits/sec for D1 & D5, 155mBits/sec for D2 & D3) required manual tracking for record like 1" the DVW-series 1/2" Digi had a pilot tracking tone system that allowed the machine to track itself for record. It could even do an insert edit if the control track was damaged by driving the phase of the scanner-lock based on the difference in signal strength between the pilot tones and the head and tail of each video track. Consequently I rarely saw machines that made incompatible recordings (that was a constant feature of all the earlier digital VTR formats).  The DVW was also the first machine to feature a Viterbi decoder in the bitstream path off tape and so you tended to get a green channel light (no error correction or concealment) until 1800hours of tape wear and then over a couple of days it would go to orange (error correction) to red channel condition (error concealment). Compared to all those earlier formats (I used to clean the heads on D1 & D2s every day of use!) they had a very low TCO.
• BetacamSX;
• DVCPro / DVCam / miniDV;
• IMX;
• HDCam;
• HDCamSR;
• Umatic;
• VHS;

Quick & dirty RS422 VTR control from your laptop

If you need to control a deck (or test routes through an RS422 matrix) then a very quick and easy way of doing it is via your laptop. Modern machines don't have RS232 ports and so you can't just hook up an RS232-422 balancer, but USB serial devices are cheap - the Addenda RS-USB4 is the one I keep in my rucksack.

It's worth noting some of the settings you need for the serial port in Windows.

You then need a bit of software that will talk the P2 protocol. WSony II has been around forever but still works under Windows7. You have to run it as admin for it to access the serial port.

Once it runs you have to tell it what port number gave it - It shows up as Com1 on my machine by default, but bear in mind that Windows will often assign it to Com5 or greater. The WSonyII will only talk up to Com4 so you might need to change that (see the first image above in the advanced tab).

Now you've got everything you need to drive a VT or test that an RS422 circuit is working.

Oh, if you don't have the CD that came with the Addenda adaptor cable you'll need to download the software here.

Remember; P2 over RS422 runs at 38,400 baud.

Broadcast Engineers of a certain age - enjoy!

I'm prep'ing a BVW-75P for training (yes - some people still want to know how to fix VTRs!); here are some pictures.

Synchronous ain't always best!

Engineers have been trained since time immemorial that with multiple sources of video the best thing is that they are always locked together and timed to a common reference - ideally station black & burst (or TriSyncs nowadays). The reasons for this are numerous, but a couple;

1. Studios cameras into a vision mixer have to be locked to achieve clean cuts between the cameras - it would look rubbish if you had a frame roll every time you cut between sources. The same is true of sources into a continuity suite etc.
2. In the case of Avid for the longest time you had to make sure the VTR was locked to the same reference as the Media Composer (all the way from v.7 ABVB systems in the mid-90s to the last revision of Adrenaline in 2007!) otherwise the audio and video capture portions of the machine would free-run WRT each other and within minutes you'd be loosing frames of sync.

So - I had a coffee and chat with a pal this morning who works for a big facility that has won an archive digitising project and they are using the BlackMagic DeckLink 4K card to allow them to ingest 4 x DigiBeta tapes at once. The capture software is ToolsOnAir and they found that after the first clip was captured the second clip would be a frame out of sync, and progressively worse after that - unless you re-booted between captures! It turns out that if the four VTRs are allowed to free-run then you don't get the problem. Perhaps processing the vertical syncs places a burden on the card/software and if it happens simultaneously on all four inputs trouble ensues?!

It reminded me of a situation with a big broadcaster who was distributing their regional variations over Astra on a single multiplex. The stat-mux was very unhappy with material that was (for the most part) identical; only the ad-breaks differed. Most video cuts occurred at the same time across all six SDi feeds. The solution was to apply a two frame delay between all the sources (so o/p 6 was now 12 frames late WRT o/p 1).

RS422 / Sony P2 protocol and serial stuff!

When running P2 protocol over RS422 (i.e. Sony VTR remotes) there is no hardware handshaking so RTS and CTS (Request To Send and Clear To Send) aren’t used; a bit like the old 3-wire XModem/YModem/Kermit protocols used in RS232 (remember RS422 is just a balanced version of RS232).

We base our RS422 wiring on the Quartz remote standard (Quartz were one of the first firms to use RJ45s & cat5 for RS422 remotes):

However – I know for certain that Probel use a different standard and many places are wired to whatever the local standard is; remember – until ten years ago most places wired ‘422 on star-quad cable rather than cat5e/6. I don’t know if current model Evertz routers have maintained the Quartz standard – I bet they have given they bought Quartz for its router business.

Whatever wiring standard is used always make sure that pins 2 & 7 are a twisted pair and likewise 3 & 8 otherwise you lose all the advantage of common-mode noise rejection that balanced RS422 brings.

Finally you need to be certain if a place is wired for chassis earth (pin 1 on a 9-pin) or signal earth (pins 4 & 6 on 9-pin). Signal earth is best as there is always a chance of earth-hum between areas when you tie chassis earths together but hopefully properly designed kit with balanced lines have the signal earth floating WRT to power/chassis ground. BUT, you have to stick with the local standard; if the engineer has wired only chassis earths you need to continue using pin 1 or even shorting pins 1, 4 & 6 at the remote end.

High Def 25Psf video

More than a decade ago when Mr Sony was developing what would become HDCam (with some small contribution from the previous 1" open-reel HDVRS analogue & digital formats) they realised that progressive video was the future but existing HD equipment (typically the BVM-D series monitors) couldn't lock to such a slow framerate (24/25/29.97 as opposed to 48/50/59.98 fields). The answer for progressively-sourced pictures was the Psf standard which makes progressive frames look like interlaced video. So as to make film people think that this was better than video they have a new name for a field - the segment. In fact Psf is interlaced video (but there is no movement between the fields) - it just shows that good old interlaced video is able to faithfully reproduce progressive pictures (but the reverse is not true as progressive video with the same frame-rate has only half the motion rendition as interlaced video).

So - let's dismiss a couple of misconceptions;

• There is no difference between a Psf signal and an interlaced signal from a technical standpoint
  
• Sending 1080 pictures via Psf doesn't degrade them in the slightest - in fact if you're laying off 1080 to HDCamSR then anything below a 5800 (in 50/60P mode @880mBits) is recording Psf!

Now then - below are screen-grabs from my trusty WFM7120. The first shows the output from a Symphony NitrisDX BOB. The footage had come from a Sony EX3 cameras recorded at 35mBits 1080/25P onto Memory Stick and imported straight into a progressive timeline. The Avid plays back Psf which the Tek shows as 1080i (for the reasons discussed above). Laying this off to HDCamSR (a 5500 deck) gives a 25Psf recording on tape. The second screen shot is the Quicktime sample movie imported into a new 25P timeline - it just serves to comfirm that the BOB output is always Psf.



This last picture is the down-convert output of a Leitch X75 which is a great little get you out of trouble box (basically does everything->everything with a few extra tricks thrown in - profanity delay etc.) but it's not a multi-frame broadcast standards converter (like a Snell & Wilcox Ukon).

Although you can't see it from this screen-grab the SD output has had it's field-dominance changed and the quality of the video ain't great. This wouldn't be an issue for VHS/DVD review copy or if it was the pre-processed feed for web-conversion but it's not suitable for SD delivery.
For that the best option (short of a £20k Ukon!) is to use the SD-downconvert from the HDCamSR machine.

Flashing STOP button in Sony VTRs

If (on a DigiBeta DVW-A500 or similair) you enable menu item 105 - Ref Alarm - the stop lamp will flash under several conditions;

• The reference signal is solid and the input video is locked but there is more than 43 video lines offset between them - the a longer period than the VTR's pre-read system will tolerate,


• The reference signal is solid and the input video is unlocked.


• The reference signal is solid and there is no input video and the deck is locked to video rather than ref


• There is no reference

Most folks assume it's down to a loss of reference - that's only the case in a minority of situations. I've been back and forth to one particular facility where they fail to understand this it's getting tedious!

Adrienne Electronics

Do you remember a BBC2 late-night show called Diners - back in 2002 anything that had the reality label attached to it got commissioned (although admittedly on very late in the evening). If you Google for it now there is scant evidence of it! I did find a John Walsh article from The Independent. Anyhow - one of the problems I had to solve for that show was using cheap Avids (software-only versions - ExpressDV back then) to capture or log live feeds with timecode. Of course the studio or OB sends you audio timecode (the kind that sounds like a fax and comes down a twisted pair cable) but all hardware-less edit stations assumed the timecode comes down the RS422 line as part of the machine control.
Adrienne Electronics do a range of really useful boxes to address these kind of problems - the AEC-Box-2 takes in audio code and has a 9-pin connector. It emulates a VTR but (being a solid box) doesn't actually play or rewind tape - it just tells the Avid it is doing so (in this case it's an Avid MCSoft with SDi Mojo). The really cool thing is that when the Avid asks for timecode down the RS422 the box returns what it is receiving on it's input. It's the ideal solution for using cheap workstations to log or capture proper studio or OB type material.
Now I'd been puzzling about this for ages last night (got home late from the studio where I was working) and it was only over my tea that I remembered solving the problem five years before - kinda like how everyone has forgotten Diners!