Answers.Body: <p>Wikipedia does <a href="https://en.wikipedia.org/wiki/SMPTE_424M" rel="nofollow">mention</a> it - with a reference <a href="https://tech.ebu.ch/docs/techreports/tr002.pdf" rel="nofollow">link</a> included:</p>
  
  <blockquote>
    <p>Within this standard there are three formats known as Level A, Level B
    Dual Link (B-DL) and Level B Dual Stream (B-DS). The Level A format is
    the direct mapping of uncompressed 1080p (up to 60 fps) video into a
    serial digital interface at the nominal 3 Gbit/s. The Level B-DL
    format is the mapping of dual-link HD-SDI/SMPTE 372M (i.e.: 1080p up
    to 60 fps) in a single serial digital interface at the nominal 3
    Gbit/s. The Level B-DS format is the dual-stream carriage of two
    independent HD-SDI/SMPTE 292M signals (720p up to 60 fps or
    1080i/1080p up to 30 fps) in a single serial digital interface at the
    nominal 3 Gbit/s</p>
  </blockquote>
  
  <p>The PDF reference has the descriptions starting on pg. 17.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-27T05:35:41.637Z
Answers.LastActivityDate: 2016-04-27T05:35:41.637Z
Answers.UserDisplayName: Gyan
Body: <p>Can someone point me at a description of the difference between a 3G-A SDI signal and a 3G-B SDI signal.  </p>
  
  <p>I have a rack with a BlackMagic ATEM 2 M/E Production Studio 4K and a bank of 3 SWT Pro-HD monitors.  The ATEM is set up to run 1080p59.94. The monitors show "No-sync" when fed from the Aux outputs of the ATEM.</p>
  
  <p>If I insert a Decimator MD-HX between the Aux output and the monitor's SDI input, it shows the SDI input to the MD-HX running 3G-B 1920x1080p59.94.
  The SDI output of the MD-HX is switchable between 3G-A SDI and 3G-B SDI. Switching he output to 3G-A makes the signal appear on the monitor.</p>
  
  <p>The problem does not appear if I run the ATEM at 720p59.94.</p>
  
  <p>Wikipedia's article on SDI does not mention the A and B variants of SDI.</p>
  
Tags: <sdi>
Title: What's the difference between 3G-A SDI and 3G-B SDI?
UserDisplayName: Richard Milewski
ThreadText: # What's the difference between 3G-A SDI and 3G-B SDI?
  
  (Asked by: username_0 on 2016-04-27)
  
  Can someone point me at a description of the difference between a 3G-A SDI signal and a 3G-B SDI signal.
  
  I have a rack with a BlackMagic ATEM 2 M/E Production Studio 4K and a bank of 3 SWT Pro-HD monitors. The ATEM is set up to run 1080p59.94. The monitors show "No-sync" when fed from the Aux outputs of the ATEM.
  
  If I insert a Decimator MD-HX between the Aux output and the monitor's SDI input, it shows the SDI input to the MD-HX running 3G-B 1920x1080p59.94.
  The SDI output of the MD-HX is switchable between 3G-A SDI and 3G-B SDI. Switching he output to 3G-A makes the signal appear on the monitor.
  
  The problem does not appear if I run the ATEM at 720p59.94.
  
  Wikipedia's article on SDI does not mention the A and B variants of SDI.
  
  **Tags:** sdi
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2016-04-27. Score: 3 | Accepted answer
  
  Wikipedia does [mention](https://en.wikipedia.org/wiki/SMPTE_424M) it - with a reference [link](https://tech.ebu.ch/docs/techreports/tr002.pdf) included:
  
  > Within this standard there are three formats known as Level A, Level B
  > Dual Link (B-DL) and Level B Dual Stream (B-DS). The Level A format is
  > the direct mapping of uncompressed 1080p (up to 60 fps) video into a
  > serial digital interface at the nominal 3 Gbit/s. The Level B-DL
  > format is the mapping of dual-link HD-SDI/SMPTE 372M (i.e.: 1080p up
  > to 60 fps) in a single serial digital interface at the nominal 3
  > Gbit/s. The Level B-DS format is the dual-stream carriage of two
  > independent HD-SDI/SMPTE 292M signals (720p up to 60 fps or
  > 1080i/1080p up to 30 fps) in a single serial digital interface at the
  > nominal 3 Gbit/s
  
  The PDF reference has the descriptions starting on pg. 17.
  
  
  ---
  
  