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Edit Review—CineForm Aspect HD

Mar 1, 2004 12:00 PM, By Steve Mullen

Realtime HDV editing for Adobe Premiere.

Now that folks are shooting HDV-format HD video with the JVC JY-HD10, they face the quandary of how to edit it. Those of you who read my story “How to Edit HDV” in the September 2003 issue know there are multiple solutions, none of which is as simple as we are used with DV25. As reflected in the chart below, it's clear that the size of the MPEG-2 file captured via IEEE 1394 is not the problem. Surprisingly, the HD files takes less space than does a DV25 file. The captured MPEG-2 transport stream requires only about 9GB of disk space per hour of footage. Of course, this makes sense because the 720p30 data stream uses only 19Mbps vs. 25Mbps for DV. (When 1080i HDV arrives, it will work at 25Mbps.)

Working within Adobe Premiere Pro, Aspect HD uses an intermediate codec to edit HDV-format video.

Currently, only the KDDI NLE (see review, p. 55) that's bundled with the JVC HDV camcorder enables you to import, edit, and export MPEG-2 transport streams. All other NLEs require the transport stream to be externally demuxed (split) into MPEG Layer II (or WAVE or AIFF) audio and MPEG-2 video elementary streams. The demux can be done during a capture — as is the case with Aspect HD — or after the capture.

Therefore, we can categorize HDV editors into those that work directly with the MPEG-2 Transport Streams and those that do not. Those that do are “native” HDV editors. Those that do not, use one of two techniques to enable a non-MPEG-2 NLE to edit MPEG-2. These techniques involve the use of proxy video or the use of an intermediate format. Those with long memories may remember using proxy video with Premiere 4.2. My HDVcinema (www.mindspring.com/~d-v-c) transcodes demuxed MPEG-2 to proxy video to enable realtime editing with Final Cut Pro. Proxy video requires less than 1GB per hour. After editing, but before export, proxy clips are replaced by HD MPEG-2 clips.

Depending on system speed, Aspect HD can edit up to four HD streams in realtime, with multiple effects per stream.

The use of proxy video is the basis for all “offline/online” editing procedures. Film editing using video is an example of the use of proxy material.

The use of an intermediate format is quite different. Here the edit is performed online using video that has the same spatial resolution as the original, yet is substantially different. Three types of intermediate codecs can be used: lossless, mathematically lossless, and lossy.

By converting the demuxed MPEG-2 to either 8-bit or 10-bit uncompressed video, one is able to edit using a lossless intermediate.

Uncompressed files, unfortunately, are huge at nearly 300GB per hour of footage. Moreover, uncompressed HD video requires a RAID in order to play back smoothly at normal speed. There are several codecs that are claimed to be lossless. These include “Huffyuv” for the PC (www.afterdawn.com/software/video_software/codecs_and_filters/huffyuv.cfm) and the “DC30” codec for the Mac (www.alfanet.it/squared5/dc30xact.html).

CineForm (www.cineform.com) has developed a twist on the use of an intermediate codec by developing an HD rendering engine for its codec. Therefore, Aspect HD is far more than a YAC (Yet Another Codec) approach. This combination technology puts CineForm way ahead of the competition in the ability to edit complex HD timelines in realtime.

The company's Aspect HD plug-in for Premiere employs an intermediate codec it calls CFHD, which is based on Wavelet compression. To increase editing performance, the algorithms within the company's Carlsbad software processing engine take advantage of video that's stored in a format that allows more efficient retrieval from hard drives — and whose compression format allows for very efficient video effects processing by exploiting Intel SSE2 instructions.

The Aspect HD bundle includes an HDV I/O application for i.LINK transfer. The version I tested forced you to convert each capture clip from MPEG-2 to CFHD after capture via i.LINK. The new version, now shipping, uses an on-the-fly conversion process. If the Pentium 4 in your PC is 2.8GHz or faster, data is converted directly into a file that occupies 33GB of space per hour of video. If, however, you have a less powerful Pentium 4, the capture goes into an intelligent buffer that is emptied as fast as the conversion occurs.

Because timecode is not sent from the camcorder while MPEG-2 is captured, you cannot set in/out points for capture using the i.LINK HDV I/O application. This prevents batch capture and re-capture. Moreover, video and audio are not presented on your RGB monitor during capture. You can capture multiple shots into a single clip, but whenever a loss of valid data is encountered, capture continues into a new clip.

CineForm emphasizes that CFHD was designed to be a very high-quality intermediate codec operating in a 4:2:2 color space. Quality is high for two reasons. First, because low data rate (19Mbps) HD MPEG-2 is decoded and then recompressed with a high data rate (80Mbps) codec, quality is claimed not to be lost during the capture/conversion process. (SD 480p60 is not yet supported.) Second, because video is only lightly compressed (typically 6:1), during editing it behaves more like uncompressed than compressed video. Let's look at the latter concept more closely.

CineForm maintains that CFHD by its nature does not cause any measurable loss in quality. In fact, in a white paper on its website (www.cineform.com/technology/default.htm) the company maintains that using CFHD as an intermediate codec actually improves image quality over editing “MPEG-2.” CineForm admits this is counterintuitive but argues, “…even simple productions will manipulate the video using image processing operations such as color correction, overlaid titles, and transitions. Each manipulation requires that the video be decompressed, modified, and then recompressed, which introduces a quality loss.”

The white paper makes a questionable general claim about the requirement that MPEG-2 video must be repeatedly decompressed and recompressed during editing. Thankfully, modern NLEs do not necessarily work this way. Each video stream is uncompressed to digital video once, mixed with other uncompressed video streams — and displayed during editing or recompressed once during export. Therefore, all effects are generated in the uncompressed domain — even if you are not aware this is happening.

Clearly, uncompressing MPEG-2 to another codec, then decompressing this for effects, and finally re-encoding the video to MPEG-2 (or another format) cannot increase quality. This observation is supported by the fact that CineForm's i.LINK HDV I/O application offers you the option of engaging “Large File” mode (100Mbps) to improve image quality.

The fundamental value of the CFHD codec is that it supports very fast decompression when applying effects.

CineForm, perhaps aware that editors might feel uncomfortable about using an intermediate codec as more native MPEG-2 NLEs come to market, is working on advanced codecs that will be mathematically lossless. Matrox has used this clever approach in its DigiSuite products. (I'm getting that DV déjá vu all over again.)

If we agree that the benefit of either an intermediate or proxy format is realtime performance, just how hot is Aspect HD? Before talking about “how many streams” you can edit in realtime, let's look at what effects are supplied. On the Aspect HD filter list, you will notice two color effects. Color Correction controls brightness, contrast, saturation, and hue, plus red, green, and blue components. The Color Balance filter adjusts red, green, and blue components in the shadow, midtone, and highlight regions. It includes an option to control total luminance level as component adjustments are made.

Aspect HD includes two 3D video effects: Pan, Zoom, Rotate (PZR) and PZR Constrained. PZR supports zoom into, pan across, and rotation of the video frame in realtime — with keyframing. It is possible, however, to rotate or pan a video clip and get black corners or edges. PZR Constrained prioritizes the parameters that prevent black corners or edges. (Editing 3D effects for high-definition video in realtime is an astounding experience.)

Many Aspect HD users will output primarily to standard-definition video. Since the HD source has much higher resolution, zooming in a reasonable amount does not affect final quality. For example, a wedding videographer could set up a stationary camera at the back of the chapel. Then during post, he could zoom closer to the couple at the altar.

Aspect HD also supports realtime Premiere transparency control, realtime alpha channels on 32-bit TGA images, and realtime Premiere motion effects. Aspect HD also includes a Force Render filter that renders all effects over the duration of the clip. Realtime keys are not yet supported.

Realtime transitions standard with Aspect HD include dissolves, page turns, pushes and covers, plus over 30 wipes. Like Premiere transitions, Aspect HD transitions have Custom settings. And, although they will not be realtime, all Premiere transitions and effects can be used.

Aspect HD supports the application of multiple realtime effects to each video stream. Thus it is possible, for example, to pan across a color-corrected clip. As long as your computer has adequate processing power, the stream will play in realtime. (Playback performance degrades as the load becomes too great.)

CineForm recommends PCs with Pentium 4 processors that support Hyper Threading working with an 800MHz front side bus. The PC should use pairs of PC3200, 400MHz, dual-channel DDR (double data rate), SDRAM DIMMs. A 2.4GHz P4 can handle two HD video streams using a single ATA100/133 7200rpm drive. Aspect HD can handle up to four streams of HD if you use a 2.8GHz P4 with a software or hardware RAID. CineForm reports that a 3.2GHz P4, working with an Intel 875P chipset plus a SATA motherboard-based RAID, can handle up to six streams. I tested Aspect HD on a 2.8GHz PC (with hardware SATA RAID) supplied by Applied Magic (www.applied-magic.com).

If your PC has a Matrox Parhelia or P750, you can send letterboxed video from the timeline to an NTSC monitor. Alternately, to view quasi-high-def, simply locate Premiere's Program window on a second or third SXGA (1280×1024) desktop, then feed this signal to an HD plasma or projector.

Once you have edited your HD production, there are multiple export options. Two HD options are Windows Media 9 and MPEG2-TS. Windows Media now supports high-definition encoding and playback. This enables your HD production to be played on a reasonably fast PC. By playing on a PC, the full resolution is available for viewing on the PC, a plasma screen, or via a video projector.

To output your HD production back to an HDV camcorder or to a D-VHS deck for distribution, first export using the MPEG-2 Transport Stream format. Aspect HD includes a HD preset for the included MainConcept MPEG-2 encoder. Every frame must be decompressed from CFHD and recompressed to MPEG-2 TS, which makes export a time-consuming process. When an export is done, use the Aspect HD i.LINK HDV I/O application to output the TS file.

Aspect HD is available directly from CineForm for $1,199. The current version supports Premiere Pro. If you still have Premiere 6.5, you can buy the previous version for the same price.

Some users report problems connecting JVC i.LINK devices to their PCs. Unlike OS X, under which the JVC devices are automatically recognized, Windows XP forces you to use the New Hardware Wizard. I strongly recommend you download a detailed “How to Install Drivers” document (available at http://supportcenteronline.com/ics/support/default.asp?deptID=614) before plugging in your JVC devices. In my tests, Aspect HD was rock-solid day in and day out.

Not only is Aspect HD an impressive out-of-the gate product, it is clearly the best current HDV editing solution available. I was blown away by the ability to edit four HD streams with multiple effects per stream — all in realtime. I recommend it highly.

© 2008 Penton Media, Inc.