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Why capture HDV via HDMI?

Visual frame accuracy, picture quality, and recapturability are only some of the many advantages of HDMI capture.

By Allan Tépper | January 05, 2009

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For many reasons explained in my recent article, it makes a lot of sense to capture your HDV footage directly to an editing i-frame códec like ProRes422. One of the best way to do that nowadays from HDV is via HDMI. Editing directly from ProRes422 files (as opposed to hybrid editing or native editing, as explained in the prior article,) offers you visually frame-accurate editing, which is critical whenever your project includes:


  • Critical multilayer editing

  • Independently recorded 48 KHz audio which needs to be lip-synced



If you try to do either of those two things from your raw long-GOP HDV footage directly, you'll find that what you see is rarely what you eventually get. This has nothing to do with choosing to shoot in HDV or not; but it has everything to do with how to post-produce your HDV footage, especially when your production will include either of those two demanding facets mentioned above. (If your production includes neither of those facets, and you are very short on space, then hybrid editing or native editing would work, but you would miss out on some of the other advantages you're about to discover.)


Advantages of capturing via HDMI directly (or via HD-SDI) as opposed to other methods include:


  • Avoiding unnecessary D>A (digital>analog) and A>D (analog>digital) conversions by keeping your HD signal as digital (as opposed to capturing via component analog). Click here to see a breathtaking comparison video, courtesy of Convergent Design and JVC Italy. The same HDV 720p25 footage was captured from the same HDV tape both via component analog HD and via HDMI>HD-SDI, and compared. This video is in 1280x720 in WMV. If you are on a Mac and have not done so yet, please download Flip4Mac's free WMV component for QuickTime here, which will allow you to see WMV in your QuickTime Player.

  • Taking advantage of the HDV deck's correction circuit (which is unfortunately bypassed via IEEE-1394).

  • You can get a more universal HDV player (see details later in the next article, Universal HDV deck, coming January 8th).

  • You can save time and space (as opposed to capturing via 1394 and converting later)

  • You retain Log & Capture, deck control, original timecode, and (as a result) recapture capability (as opposed to using FCP's HDV-ProRes422 capture preset via 1394, where you sadly lose all of these four features)

In case you didn't know, the HDMI interface was designed to transport uncompressed digital video signals (both standard definition video and full-raster high definition video, either at 1280x720 or at 1920x1080), with optional digital audio. With those features and quality, HDMI rivals both SDI and HD-SDI in many applications. There are differences, but few.

A few years ago, we saw HDMI outputs start appearing on certain DVD players and HDV decks, like JVC's BR-HD50… and more recently on some of Sony's HVR series HDV decks. Several HD camcorder manufacturers have added HDMI outputs, including Canon (consumer only... so far), JVC (consumer only... so far), Panasonic (consumer & professional), and Sony (consumer & professional). Also, several non-linear hardware manufacturers have added an HDMI output for monitoring. At the beginning, these HDMI outputs were destined to be connected exclusively to HDMI monitors, since no video production or post-production device had an HDMI input, until... (see page 2!)

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Comments

R_Andreu: | January, 05, 2009

This is a great article. Understanding all the facts of video capturing is a little bit difficult. The amount of resolutions, frame/field frequency, the different codecs doesn’t helps either. It’s important to have a place were we can have basic and advanced information (and growing!) about those important issues.

Thanks to Provideo Coalition and specially to Mr. Allan T

DanConklin: | January, 05, 2009

Does HDMI capture preserve the date and time codes?

Allan T: | January, 05, 2009

Thank you R_Andreu!

DonConklin: HDMI by itself does not. However, you will discover ways to preserve that information in the upcoming article: “Controlling HDV when capturing HDMI” on January 12th. Stay tuned!

Lanceishere: | January, 05, 2009

So, if I have a Canon XH-A1 and put the HDV tape from it into a Canon HV-30, which has an HDMI out, then I can import into a mac pro or macbook pro with another HDMI card, and get the benefits described?

Is there another way to do this from my XH-A1 HDV tape?

Allan T: | January, 05, 2009

Hello Laceishere,

It will work, although if what you shot in the XH-A1 is “24f”, it would play as 59.94i (“60i”) on the HV30’s HDMI output, as explained in the articles. To play or ingest footage shot in the XH-A1, you could use any of the Sony decks mentioned (HVR-M25A, HVR-M35).

Jamie: | February, 13, 2009

hello - I don’t understand the benefits of hdmi capture vs firewire - shooting on a z7u I understood that after it’s on tape there is no real benefit to capturing via hdmi as the footage is already compressed - certainly better hdmi than component but why not just use firewire?
thanks

Allan T: | February, 13, 2009

Jamie,
When you compare FireWire with HDMI, you are correct: there is no benefit in picture quality. However, there are several other advantages as explained in the article, whenever your project includes critical multilayer editing and/or independently recorded 48 KHz audio which needs to be lip-synced. If you try to do either of those two things from your raw long-GOP HDV footage directly, you’ll find that what you see is rarely what you eventually get. Please re-read the article in order to understand the incontrovertible reasons why, and the undisputable advantages of capturing via HDMI or HD-SDI directly to an i-frame códec in those cases. Yes, they have nothing to do with picture quality (when compared with FireWire), but they indeed matter in many cases. By the way, if you read my “Sony upgrades 3G HDV camcorders to universal” article, you’ll see how you can upgrade your Z7U to world-class compatibility.

Allan T

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