• Compression Techniques

  ProRes 720×486 Black Lines

  Posted by John Michaels on December 7, 2015 at 6:23 pm

  Hello, hoping for a sanity check here.

  I’m taking a lot of 1080p 23.976 HD masters and center cutting them down to 720×486 23.976 SD ProRes files (just following orders). When I do this, I get black lines at the top and bottom of the frame.

  Now, my understanding is that these black lines should be there; it’s the VBI, correct? My files keep getting rejected by the powers that be, because of those black lines. However, the client is also explicitly asking for 486 and not 480 so I can’t just go that route.

  I did notice that if I bring the files in to Final Cut Pro or view them in Quicktime 7, that the black bars remain, instead of being somehow “hidden” as would happen with another SD format such as IMX50. Is it possible this is just a metadata issue of some sort?

  Attached is a frame grab, and below is a mediainfo readout of the file:

  

  General
Complete name : /Users/JohnMichaels/Desktop/test.mov
Format : MPEG-4
Format profile : QuickTime
Codec ID : qt
File size : 53.2 GiB
Duration : 2h 6mn
Overall bit rate mode : Variable
Overall bit rate : 60.2 Mbps
Encoded date : UTC 2015-11-23 17:45:58
Tagged date : UTC 2015-11-23 17:45:58

  Video
  ID : 2
  Format : ProRes
  Format version : Version 0
  Format profile : 422 HQ
  Codec ID : apch
  Duration : 2h 6mn
  Bit rate mode : Variable
  Bit rate : 48.6 Mbps
  Width : 720 pixels
  Clean aperture width : 720 pixels
  Height : 486 pixels
  Clean aperture height : 486 pixels
  Display aspect ratio : 4:3
  Clean aperture display aspect ratio : 4:3
  Frame rate mode : Constant
  Frame rate : 23.976 fps
  Color space : YUV
  Chroma subsampling : 4:2:2
  Scan type : Progressive
  Bits/(Pixel*Frame) : 5.798
  Stream size : 43.0 GiB (81%)
  Title : Telestream Inc. Telestream Media Framework - Release TXGP 2015.12.176624
  Writing library : apt0
  Encoded date : UTC 2015-11-23 17:45:58
  Tagged date : UTC 2015-11-23 17:45:58
  Color primaries : BT.601 NTSC
  Transfer characteristics : BT.709
  Matrix coefficients : BT.601
  matrix_coefficients_Original : BT.601

  Audio
  ID : 3
  Format : PCM
  Format settings, Endianness : Little
  Format settings, Sign : Unsigned
  Codec ID : in24
  Duration : 2h 6mn
  Bit rate mode : Constant
  Bit rate : 11.5 Mbps
  Channel(s) : 10 channels
  Sampling rate : 48.0 KHz
  Bit depth : 24 bits
  Stream size : 10.2 GiB (19%)
  Title : Telestream Inc. Telestream Media Framework - Release TXGP 2015.12.176624
  Language : English
  Encoded date : UTC 2015-11-23 17:45:58
  Tagged date : UTC 2015-11-23 17:45:58

  Other
ID : 1
Type : Time code
Format : QuickTime TC
Duration : 2h 6mn
Time code of first frame : 00:57:30:00
Time code, striped : Yes
Title : Telestream Inc. Telestream Media Framework - Release TXGP 2015.12.176624
Language : English
Encoded date : UTC 2015-11-23 17:45:58
Tagged date : UTC 2015-11-23 17:45:58
Bit rate mode : CBR

  Craig Seeman replied 10 years, 6 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Craig Seeman

  December 7, 2015 at 7:18 pm

  Quicktime 7 Player (and Frameworks) are deprecated.

  Please test in Telestream Switch 2.0.1 and Quicktime X.
  Please explain exactly what your settings are in the Resize Filter (be complete).
  What version of Episode are you using (current is version 7).
  Also please do describe intended use of the encoded file.
• 

  John Michaels

  December 7, 2015 at 7:22 pm

  Same thing in Switch an Quicktime X.

  I’m doing this in Vantage (not Episode) using the Quicktime (Telestream) encoder. For my Resize filter, I’ve tried both “Crop (Center Cut)” and Manual, with 0 crop and padding on top and bottom, and 240 pixel crop in from left and right. Both resize settings yield the same result. I do have the VBI settings enabled (which is the default) for 4 upper and 2 lower. I’m sure disabling this (setting it to full frame active picture) would get rid of the bars, but again, aren’t they supposed to be there for 486 material?
• 

  Craig Seeman

  December 8, 2015 at 5:00 am

  [John Michaels] “I’m sure disabling this (setting it to full frame active picture) would get rid of the bars, but again, aren’t they supposed to be there for 486 material?”

  I think you should get rid of the bars especially if that’s what they want. As to the 6 lines, HD to SD conversion can involve going to 720×480 source and one would need to add the lines (4 on top, 2 bottom as you mention) to get a 486 standard for broadcast. Those lines wouldn’t be visible due to TV overscan.That wouldn’t be VBI though. It its not for broadcast it can be left at 720×480 (DVD for example).

  This is why I wonder what the intent is. Might there be a next stage where someone will add pull down frames and interlace? If it’s for DVD use 720×480 would be fine. In fact one might do 720×480 anamorphic for SD 16×9 to keep the aspect ratio.

  VBI would be 720×512. This is how I would deliver SD broadcast spots back in the day to DGFastchannel for distribution.

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