HDV Capture Setting: “MPEG Video Quality”

[Tyler Seboe]

Geo Brick,

Sorry to ressurect a 10 month old thread and I don’t know if you found an answer regarding the quality setting question on capture but I had the same question and it took some searching. It is amazing that neither the documentation provided with my version of Vegas nor Sony’s online support reference this and many other settings at all. Others have commented that Sony ironically writes its user guides assuming the end user is an expert…why bother?

Indirectly quoting numerous posts by John Rofrano, who is very helpful, Sony Vegas captures from firewire bit-for-bit–essentially acting as a file copy from your camera to your hard drive. The “MPEG video quality” setting seems to be disabled (although not greyed out) when capturing via firewire. If you wish to verify this, do a capture of a short clip with various quality settings (my maximum is 31 in Vegas Movie Studio HD Platinum 10.0) and you’ll find the file size to be identical. I don’t know if the same is true if you connect via USB (if possible with your camera) because I’ve never tried it.

Incidentally, a 60 minute HDV clip from my camera, a Canon HV20 recording in 1440×1080 (pixel aspect ratio is 1.33:1 so 1.33×1440=~1920 thus this is “true” HD 1920×1080 once the 1440 is “stretched”) at 25 Mbps (megabits per second) or 3.125 MBps (megabytes per second), should be about 11.5 GB. These figures are indirectly quoted from this discussion thread: https://www.avsforum.com/avs-vb/showthread.php?p=19382341 and I’m trusting other people’s math although empirically my files are all about that size (I think we actually get 63 minutes per HDV tape).

Mr. Rofrano alluded to the quality setting relating to analog capture but I did not verify this nor do I fully understand it or ever intend to use it.

Your m2t vs. mpeg question leads to a long discussion but the basics are easily discerned on Wikipedia’s entries for m2ts, HDV, and MPEG-2.

I’m guessing that Windows 7 “calls” it AVCHD because many of the newer consumer video cameras that write to hard drives, DVD, and/or solid state memory record files using the AVCHD format which utilizes an MPEG-2 transport stream (thus outputs .m2t files when transferred to your hard drive). Explorer must assume it’s AVCHD because its popular now. Interestingly, once I changed my default media player from Windows Media Player to VLC in Windows 7, the file type shows as m2t and not AVCHD.

Hope that helps somebody,

Ty

[Geo Brick]

Thanks for the response. I also gathered, through several other posts on the web, that the quality setting is functionless with the firewire capture of HDV data.

About 1440×1080; I wouldn’t call the stretched version “True” HD 1920×1080. By stretching it, you don’t get a pixel to pixel map. It’s an anamorphic process. I’m not sure of the processing involved, but when 1440 pixels are being stretched across 1920 pixels, it’s not True 1920. The process to map the 1440 across 1920 pixels when restoring the aspect ratio is done in a way that makes it hard to tell (maybe it alternates, by line which pixels get streted. Who knows?). It still looks great and depending on lens and sensor quality, it could be as good or better than some true 1920×1080 cameras.

[Tyler Seboe]

Agreed (that’s why i used quatation marks around true and streched”.

I will be curious though–I’m going to try editing using an intermediate (NeoScene) because I want to experiment with color correction and frame-by-frame editing on a more advanced level–if NeoScene outputs by default or gives the option to output at 1920×1080 with a 1:1 pixel aspect ratio. That answer may be readily available/obvious…it’s off the top of my head and I haven’t researched if it even makes sense.

Thanks for getting me thinking!

ty