HDV editing using Avid’s Liquid 7.1, Part 2

Jul 24, 2006 12:09 PM, Steve Mullen

In the last installment, I asked “What would it mean to your HDV editing workflow if you could insert multiple video formats into a Timeline?” We then began to examine this question by looking at Avid’s Liquid 7.1. I remarked that I created two HDV sequences using Liquid.

One sequence was created as HDV 720p30 and the other sequence was created as HDV 1080i60. The 720p30 sequence contained 720p30, 720p24, 1080i60, 16:9 DV, 4:3 DV, and QCIF MPEG-1. The 1080i60 sequence began with multiple Sony Z1 clips followed by the entire 720p sequence. I had simply dragged the 720p sequence from Liquid’s Sequence Rack (Bin) into the 1080i sequence.

In this installment, we will look at how I acquired the various source material used in these sequences. I captured, via FireWire, the 720p30, 480p60, 1080i60, 4:3 DV, and 16:9 DV. The QCIF MPEG-1 was imported from a file transferred from my cellphone, and the 720p24 was located on a Focus DR-HD100 hard drive.

Let’s look at how I captured these different formats. If you're working with Final Cut Pro, choose a Capture Preset for each video format you want to capture. If you have 720p24 video, you are currently out of luck because Apple has not yet provided a native HDV preset for that.

Liquid operates very differently. You begin by selecting the Rack you want to hold the captured clips and then select either the EZ Capture Tool or the Logging Tool. As you might guess, the latter tool has the capability to capture a marked video segment, log a segment, or batch-capture the logged segments.

Tip 1: Because the first-generation HDV 720p camcorder does not have timecode embedded in the M2V data stream, the tapes should not be used with the Logging Tool.

Unless one’s PC is storage-limited, there is really no need for the Logging tool, as the EZ Capture Tool will do all that is necessary to capture an entire tape. For this reason, I used the EZ Capture Tool for all my FireWire input. (Including 1394 capture from the Focus DR-HD100.)

When you bring up the EZ Capture Tool you can use the VTR control to locate the point(s) at which you want the capture to begin. Note I did not select a Capture Preset. Why not? From my point of view, the real question is why do I need to do so with other NLEs? One should not need to do so, given FireWire’s inherent functionality. When a device is connected, software interrogates the device. The device responds with its brand and model number. From this information the software can alter its communication protocol, if necessary, to match the device.

Tip 2: You do need to select the device brand when using the Logging Tool in Liquid. You also have the option of “Live 1394 Capture,” which allows you to add Time-of-Day Timecode to the recording.

The software also checks whether the device is set to send MPEG-2. (HDV devices have a switch that is set to either DV or MPEG-2.) So there is no need for a human to tell the software this basic information. But what about the type of DV or HDV?

Both DV and HDV bit streams carry detailed information about the nature of data carried by the streams. This information tells the software the frame size, aspect ratio, timecode base, frame rate, and interlaced/progressive status. Using this information, the software creates a header for the data that will be moved to a disk file during capture. Thus, once again, there is no need for a human to tell the computer what the computer can learn for itself.

Although 720p24 is not officially supported in 7.1, the software can discover that the timecode base is 59.94fps. The Repeat Flags carried in the data stream are stored to disk along with the M2V data.

Tip 3: Although first-generation JVC HDV devices are capable of outputting 24p via FireWire, Liquid erroneously rejects this data. Of course, since 24p is officially unsupported, this could be fixed in 7.2. Therefore, only (second-generation) JVC ProHD equipment can currently, and unofficially, be used to playback 24p.

Importing video is just as simple. It made no difference whether I selected a file on my PC’s hard drive or on the Focus drive. During import, the software “auto-sensed” the nature of the video. When you import from a mounted drive, such as the Focus HDD, you are given three options: Linked, Copy, and Move. The first option supports the DR-HD100’s DTE capability as all files remain on the Focus HDD. The second and third options copy or move the files to your hard disk, respectively.

Note that there is no need for video to be “converted” during import. A Liquid Timeline can hold most any type of video: DV and DVCPRO (both can be input and output via FireWire, including transfers from P2-based camcorders), DVCPRO 50 (file import and export only), XDCAM and XDCAM HD (using FireWire-based File Access Mode via Liquid’s XReceive/Xsend capability), MPEG I-frame (IMX), MPEG IBP including HDV, Windows Media, DivX, and MPEG-4, as well as SD and HD 4:2:2 uncompressed video. While SD MPEG-4 is supported, it appears HD is not. Likewise, neither DVCPRO HD nor any of the new AVC codecs are supported for either import or capture. (It would be ideal if the DVCPRO HD codec were available for FireWire export.)

Liquid Pro, which includes an analog SD breakout box for I/O, adds support for composite, Y/C, and SD component I/O. This BOB connects via a USB port so it can be used with a laptop. It is ideal for those who need to work with Beta SP — especially for the export of SD versions of HD productions.

Liquid Chrome employs a PCI card and an SDI/HD-SDI BOB that supports four embedded and AES/EBU digital audio channels. Using HD 4:2:2 uncompressed video, this option provides support for HDCAM, DVCPRO 50, and DVCPRO HD.

After capture or import, Scene Detection can be employed to divide a clip into subclips. This feature worked perfectly with both DV and HDV.

Tip 4: Be sure to request Master subclips and specify handles of at least one frame. By providing handles, Liquid’s Consolidate capability can be used when a project is complete. This function will retain only the video used by the project while removing all unused media. The result can be stored to DVD or, in the future, to Blu-ray discs.

In the next installment, we will explore how all these various formats can be used in a sequence and how a very wide range of productions can be automatically generated from a mixed-format sequence.

Below you will find updated images of my customization of Liquid’s interface. Immediately below is the main editing interface.