Digital Video - November 2007 - (Page 49) EVEN THE BEST ORIGINATING PICTURE FORMATS—SUCH AS HDCAM, FILM, AND CGI—CAN REVEAL GLARING ARTIFACTS WHEN VIEWED ON A LARGEENOUGH SCREEN. decisions about where to distribute bits within a shot, and where to set I-frames. You can tweak a parameter called Adaptive Quantization at this point, but in most cases you’ll wait until Step 5 (segment reencode). 4. REVIEW THE BASE ENCODE. Like MPEG-2 encoding, you visually inspect the entire film on a scene-by-scene basis. But, unlike standard DVD, you carefully review a detailed bitstream analysis created by the encoder application. 5. REENCODE SETUP. Some specific scenes may need improvement. Besides looking for artifacts you also check the status of the video buffer, in order to make sure that you’re not feeding it too much bandwidth. At this stage with the Sonic system, you may decide you need additional Digital Vision processing to deal with noise specific to one shot. Aside from that, you’ll mainly be playing with quantization and motion search parameters. 6. REENCODE RUN. Run as many different re-encode takes as you need, and choose the best one which avoids buffer problems. 7. FINAL DECISIONS. Tell the encoder which segment to keep, which will cause the app to insert it into the base encode, replacing the unwanted original pass. DRILLING DOWN Let’s take a close-up look at segment reencoding with the AVC/H.264 codec in CineVision 2.0 (a product that also does HD MPEG-2 and VC-1 encoding). First you analyze the base encode, by looking at the various status tracks in the timeline, including quantization. You can use Sonic’s ExpressQC function to automatically detect sections of the encode that have a low peak signal to noise ratio. You’ll also want to do a careful visual inspection on a large HD monitor, to look for blocky artifacts. Now that you have identified problematic segments, you need to mark them. This is done the same way you’d do it in a nonlinear editor: the “I” key marks the in-point, and the “O” key marks the out-point. ExpressQC automatically selects ADVERTISER INDEX COMPANY AJA Audio-Technica Avid Azden B&H Blackmagic Design Calumet Canon USA Video Electronic Mailbox Full Sail MOTU Matrox Panasonic Broadcast Systems Sonnet Technologies Sony Creative Software PAGE 33 16 5 14 57-59 13,15 23 2 25 12 68 7 19 11 9 WEBSITE www.aja.com www.audio-technica.com www.avid.com www.azdencorp.com www.bhphotovideo.com www.blackmagic-design.com www.calumetphoto.com www.usa.canon.com/HD www.videoguys.com www.fullsail.com www.V3HD.com www.matrox.com/video www.panasonic.com/broadcast www.sonnettech.com www.sonycreativesoftware.com COMPANY INDEX 16x9 20; ACCOM 16; Adobe 24; Anton Bauer 22; Alien Skin 24; Apple 11, 24, 30, 31; Being Seen 43; Blackmagic Design 17, 18; Chrosziel 20, 21; Cinetech 21; Cinevate 21; Da Vinci 16; Digital Anarchy 24; Digital Vision 45, 48; Dolby 45; Element Labs 42; Fnord Software 24; Google 24; Iconix 10; Kino Flo 42; Litepanels 40, 41; Microsoft 24, 45, 46, 48, 49; NewTek 24; OnOne Software 24; Panasonic 6, 30, 31, 37, 38; Petroff 21; Philips 14; Rank Cintel 16; RED Digital Cinema 11; Redrock Micro 21; Sonic 45, 46, 48, 49; Sony 8, 10, 19; Sorenson 44; SteMan 21; Strata 24; Telestream 44; Tiffen 24, 26, 27; Vertus Software 24; Vinten 10 http://www.aja.com http://www.audio-technica.com http://www.avid.com http://www.azdencorp.com http://www.bhphotovideo.com http://www.blackmagic-design.com http://www.calumetphoto.com http://www.usa.canon.com/HD http://www.videoguys.com http://www.fullsail.com http://www.V3HD.com http://www.matrox.com/video http://www.panasonic.com/broadcast http://www.sonnettech.com http://www.sonycreativesoftware.com
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