Tech Tip - CableLabs VOD Encoding

Creating CableLabs Video

 

PixelTools PC HD encoders ExpertHD and MPEGRepairHD can encode an AVI or MOV file or a sequence of TGA, BMP or YUV frames into a CableLabs compliant High Definition (HD) and Standard Definition (SD) MPEG-2 stream.  Also, the HDProQT QuickTime export component, available for Mac and PC, and can export CableLabs streams from any Mac or PC application that recognizes QuickTime components such as Adobe AfterEffects, Final Cut Pro, and the Mac QuickTime Pro Player.

On a PC

Download the file PtCableLabs.zip file to obtain configuration settings (ini files) that configure ExpertHD and MPEGRepair to generated VOD streams.  The PtCableLabs.zip file also includes screen shots of compliant configuration options for HD and SD when using the PC HDProQT QuickTime Export.

To encode Cable Labs content using MPEGRepairHD or ExpertHD, select the “Base Encoding Profile | Load Custom ini file” option as depicted below. Select the appropriate ini file from the PtCableLabs.zip file to configure the tool to appropriate Cable Labs settings. Depress the Optimize Encode | Configure |Audio/Mux dialog and browse to your AC3 file in the “Mux Compressed Audio File” edit box.   Select your Encode Input and Encode Output files and depress the Control Encode | Run button to start the processing.  The encoder should compress your source video and then multiplex the video with your AC3 audio file per Cable Labs specifications.

On a Mac

To encode Cable Labs content using the HDProQT on Mac or PC, select the PixelTools HD MPEG Export option. Depress the “Options” button and configure the settings as depicted above.

 

Specifications

PixelTools HD encoders comply with CableLabs specification

MD-SP-VOD-CEP2.0-I02-070105
Issued 5 Jan 2007

The PixelTools configuration settings will produce video with the following specifications:

High Definition:

  • Multiplexed Stream:
    • MPEG -2 Transport
    • 481 Video PID
    • 482 Audio PID
    • 19.0 mbps
  • Video:
    • MPEG-2 Elementary
    • 1920 x 1080i frame size
    • Main Profile | High Level
    • 16:9 Aspect
    • 29.97 or telecine
    • M = 3
    • N = 15 for 30 fps
    • N = 12 for 24 fps
  • Audio:
    • Dolby AC3
    • DVB MPEG optional for outside of US
    • 384 kbps Dolby 5.1 or 192 kbps for two channel stereo

Standard Definition:

  • Multiplexed Stream:
    • MPEG -2 Transport
    • 481 Video PID
    • 482 Audio PID
    • 3.75 mbps
  • Video:
    • MPEG-2 Elementary
    • 720x480 frame size
    • Main Profile | Main Level
    • 4:3 Aspect
    • 29.97 or telecine
    • M = 3
    • N = 15 for 30 fps
    • N = 12 for 24 fps
  • Audio:
    •  Dolby AC3
    • DVB MPEG optional for outside of US
    • 384 kbps Dolby 5.1 or 192 kbps for two channel stereo

Note that Cable Labs supports Standard Definition 720 x 480 full resolution MPEG streams. MPEG encoding looks awful at that bit-rate and frame size except for relatively static content.  We recommend encoding at the smaller frame width of 528 x 480 or 352 x 480 for better quality.  The smaller widths are legal under Cable Labs specification. Most set top converters provide high quality width up-scaling to 720 full with resolution during display.

Refer to the MPEGRepairHD users manual or the Expert WorkShop SDK manual for additional details on the updateable headers.

MPEGRepairHD and ExpertWorkshop SDK are trademarks of PixelTools Corporation. All other brand names are trademarks or registered trademarks of their respected holders

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