These issues were brought home a few weeks ago when a client emailed in a panic, asking whether I knew how to address a problem he was having. "What follows is a really scary problem for me," he said. "Until I know what caused this problem I’ll be going on all shoots nervous because of an unknown problem with tape."
"I recorded a bit of test pre-roll, checked the camera to make sure the test record had worked, took the tape out, and then put it back in a bit later to shoot a 28-minute show," he continued. "I used a brand new, never used, straight-out-of-the-wrapper 63-minute HDV mini tape in my HDV camera."
This isn’t a client who takes his work lightly, so what followed next meant we were going to spend some time over subsequent emails and phone calls looking at what caused the problem.
"When I attempted to play the tape back, nothing happened," he said. "No image appeared. Just blue screen. Timecode did not move. Frame count did not move, but the time clock counted down remaining minutes accurately as the tape reels moved forward as normal." The client lives in the South, so he understands the issues with humidity and takes appropriate precautions. Even so, the tape wouldn’t play. But he found out something else even more interesting.
"When I used the fast forward mode, the images appeared and played in fast forward just fine," he said. "When I used fast rewind, they played in fast rewind just fine. Therefore I know the show was indeed recorded to the tape. When I push the normal-speed play button, the image freezes for a moment, then blue screen appears. The timecode and frame count appear as normal but do not move."
Based on his description, I suggested the problem sounded like an alignment issue, but playing the tape back in another camera from the same manufacturer yielded similar results. He’d also gone one step further: Using the problem tape and the same camera, he shot test footage with the remaining 35 minutes of the tape, with no apparent recording or playback problems.
"To make things even stranger, I put this same tape back in the two cameras and did some test shooting on the remaining 35 minutes of blank tape with both cameras," he said. "The tape worked fine in both cameras, and everything in the tests went as normal. The tape worked fine!"
He spent several hours tracking down the right person in the U.S. office of the camera manufacturer, who pointed back to a tape defect and said he’d never heard of this issue before.
"All they can say is that they will send me a box to put the camera in, then I send it in for them to look at," he said. "Then they send it back, maybe with an answer, maybe not. This takes about two weeks."
Not at all an ideal situation, so he opted to send the tape to a lab. He explored some forums while he waited for the tape results to come back. He found others listing a similar issue, but no one had an answer for their problems.
In the end, an answer has never materialized, although it does appear to lean toward an alignment issue. As many EventDV readers know, to compress an HD image to match DV’s 25Mbps bitrate (or, in the case of 720p HDV, to go even smaller at 19Mbps), the HDV format uses MPEG-2 interframe compression in which it records "master" I-frames that are similar to still images or the old Motion JPEG, and then also records P- or B-frames that refer back to the I-frames. The lab results revealed that the I-frames weren’t recorded but the incomplete interim frames were, which explains how a portion of the image could be seen in fast forward or rewind.
Regardless of the specific technical problem that proved to be the culprit on this occasion, my client says he’s learned two lessons: First, he will consider the option of a disk-based recording device like the FireStore as a backup recording for highly critical shoot. Second, he will use the initial 3 minutes of a 63-minute tape to run a full pre-event recording test, including color bars.
"I learned a lesson that will stay with me on every shoot until the day I die, and if heaven needs cameramen, I’ll use it there too," he said. "These tapes are 63 minutes long for a good reason: The first three minutes are for testing! Seven seconds is not long enough for a test on longGOP formats, 30 seconds is more like it."
It's a lesson learned the hard way, but it’s one that helps remind us all of the basics.
"I really need the footage from this tape, as my reputation is at stake here," he said early in the first email of our exchange on this issue. That’s true of all of us, even if we only volunteer on our house of worship’s media team during major holidays.
Tim Siglin (writer at braintrustdigital.com) writes and consults on digital media business models and "go to market" strategies. He is chairman of Braintrust Digital, a digital media production company, and co-founder of consulting firm Transitions, Inc.