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Understanding & using the breakthrough XAVC Long GOP códec/file format

Understanding & using the breakthrough XAVC Long GOP códec/file format 1
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The third category of Sony’s XAVC is the most enticing for me.

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Allan Tépper
February 25, 2015
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[UPDATED ARTICLE] Back in 2012, Sony deployed the first version of XAVC, one that can offer color depths of 8-bit, 10-bit, and 12-bit and chroma subsampling of 4:2:0, 4:2:2, or 4:4:4. That first version is i-frame and found on very high-end cameras. Then Sony released the consumer version, XAVS S, which is Long GOP up to 4:2:0 and 8-bit and is found in such cameras as the A7S. But the most enticing version (for me) is the professional XAVC Long GOP, which offers up to 4:2:2 10-bit in cameras like the PXW-X70 at up to 50 megabit/second. More ahead…

Understanding & using the breakthrough XAVC Long GOP códec/file format 2

[UPDATED ARTICLE] Back in 2012, Sony deployed the first version of XAVC, one that can offer color depths of 8-bit, 10-bit, and 12-bit and chroma subsampling of 4:2:0, 4:2:2, or 4:4:4. That first version is i-frame and found on very high-end cameras. Then Sony released the consumer version, XAVS S, which is Long GOP up to 4:2:0 and 8-bit and is found in such cameras as the A7S. But the most enticing version (for me) is the professional XAVC Long GOP, which offers up to 4:2:2 10-bit in cameras like the PXW-X70 at up to 50 megabit/second. More ahead…

In this article

  • What’s GOP (not the political party) and i-frame?
  • 50 megabit/second = nostalgia = 6.25 megabytes/second
  • How to use XAVC Long GOP files today?
    • Apple software
    • Blackmagic’s DaVinci Resolve
    • Sony software
    • Other third party software
    • Telestream Switch
    • The temporary bottom line

What’s GOP (not the political party) and i-frame?

For those unfamiliar, GOP is an acronym which stands for Group of Pictures. Both Panasonic and Sony offer both i-frame (intra frame) and Long GOP versions of H.264. The i-frame versions compress every frame individually, and are heavier (require a higher bit rate to achieve the same picture quality) but are more easily editable with older, less capable computers and older editing software. Long GOP versions only include some of the frames completely, and in other frames include the differences that appear in subsequent frames. Long GOP versions are more efficient, and therefore can give very high quality at a much lower bit rate.

50 megabit/second = nostalgia = 6.25 megabytes/second

I remember when 50 megabit per second seemed like a very high number. It is actually a nostalgic bit rate for me, since it was used in videotape formats of yesteryear, including JVC’s D–9 (previously called “Digital S”), Panasonic’s DVCPRO50, and one particular mode of Sony’s MPEG IMX. Since then, compression algorithms have matured exponentially, so we get much more from 50 megabit per second XAVC Long GOP than we did back with the códecs used with those old videotape formats. While those old videotape formats stretched the technology of the day to squeeze out 4:2:2 8-bit out of standard definition digital video derived from the old analog formats known as NTSC and PAL, the new professional XAVC Long GOP

Understanding & using the breakthrough XAVC Long GOP códec/file format 3

(as offered in the PXW-X70 camcorder which I covered in this article) is currently able to squeeze very high quality 4:2:2 10 bit out of 1080p HD video. (This same PXW-X70 will later be capable of 4K UltraHD via a firmware upgrade, although Sony has not yet revealed whether this will be free or have a price, or what the bit rate will be.)

For those more familiar with megabyte nomenclature, 50 megabit per second = 6.25 megabytes per second. In other words, at least for acquisition, XAVC Long GOP should give us comparable recording as ProRes 422(HQ) acquisition without such heavy files in the field which can frequently be at least four times larger.

How to use XAVC Long GOP files today? (See updated information ahead.)

Using XAVC Long GOP files is not as easy as it should be so far. Here are the details:

Apple software

Unfortunately, professional XAVC Long GOP files are not yet directly readable on a system level in Mac OS X 10.10.2, nor are they yet directly readable in Final Cut Pro X version 10.1.4. Professional XAVC Long GOP files are MXF. It is true that thanks to a recent update, other Sony MXF files can now be read natively in FCP X, but sadly professional XAVC Long GOP files cannot yet be read natively. Unofficial sources suggest that sometime between now and NAB in April 2015, Apple will have updates to read professional XAVC Long GOP files natively. It is possible that a system level update may automatically provide this capability to FCP X, or it may be that an FCP X update may be required.

Blackmagic’s DaVinci Resolve

I recently published the article called Why Digital Sprockets edits video with DaVinci Resolve instead of FCP X. I just tested version DaVinci Resolve Lite 11 version 11.2.1lite002 which is the free version. I am not an operator of DaVinci Resolve, but I was happy to see that I was able to import and play a clip shot in 50 megabit per second professional XAVC Long GOP 4:2:2 10 bit in this version. (The prior version was not able to read this same clip, so Blackmagic apparently added the capability, although did not mention it in the Read Me file.)

Sony software

Although Sony offers trial software to convert/transcode, at least the trial versions I have tried don’t even read professional XAVC Long GOP files, let alone transcode them. I have requested an NFR license to determine whether the issue is only with the trial versions, but I have not yet received said license.

Other third party software

There are several third-party software that promise to transcode professional XAVC Long GOP files. So far, the ones I have tried either crash upon opening or don’t read, with the notable exception of Telestream’s Switch (which I reviewed in this article). See ahead.

Telestream Switch

The only piece of transcoding software I currently have installed in my MacBook Air that has been able to read and transcode professional XAVC Long GOP files so far has been Telestream’s Switch. The sound and picture look fine, although there was a bug which I reported and has been acknowledged and already fixed in version 1.5, which is also be available for Windows. The bug was that instead of reading the 1920×1080 file as such, it read it inappropriately as 1920×1072. Fortunately Telestream fixed it quickly.

The temporary bottom line (See updated information ahead.)

As stated earlier, it is expected that professional XAVC Long GOP files will soon be readable in Macs on a system level, and/or in FCP X. If your preferred editor is already DaVinci Resolve, then you are apparently all set. I don’t have Premiere CC to try it. If your preferred editor is FCP X, you can either (temporarily) shoot AVCHD until the situation changes, or transcode using Telestream Switch (hopefully version 1.5 or later) or even capture from the camera’s HD-SDI or HDMI output if you have the appropriate hardware to do so. When I hear of any other transcoding app or Sony plugin that works properly with professional XAVC Long GOP files, I will either amend this article or publish a new one. Likewise, when Mac OS X and or FCP X supports professional XAVC Long GOP files directly, I’ll write about that too. 

New and updated information

Since this article was originally published, several new options have appeared to transcode professional XAVC Long GOP and more editing software can read it natively. Please see these newer articles.

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In English:

Understanding & using the breakthrough XAVC Long GOP códec/file format 4

In English, it is currently available in the following Amazon stores, depending upon your region:

 

Or in your favorite bookstore by requesting ISBN–10: 1456310232 or ISBN–13: 978–1456310233.

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Understanding & using the breakthrough XAVC Long GOP códec/file format 5

En castellano, está disponible actualmente en las siguientes tiendas Amazon, según tu región:

o en tu librería preferida al solicitar el ISBN–10: 1492783390 ó el ISBN–13: 978–1492783398.

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