Tech Tip - Troubleshooting Closed Captioning with Expert-Caption

There are many opportunities for error when captioning videos. If no captions appear on a captioned video for example, the issue could be:

  • transcribed caption time-code different than that in the video
  • decoder does not support closed captioning format
  • caption insertion error

Expert-Caption includes a variety of caption analysis features that will assist you in resolving captioning issues. The tool provides visibility into the multiple layers of the captioning in your stream.

 

Quick File Analysis

  1. Drop your file to be analyzed onto the “File to Decode or Analyze” edit box
  2. Depress the Analyze button

The analysis dialog will appear.

analysis dialogue Pixeltools closed cptions

The Closed Captioning box lists all of the closed captioning channels detected. (There may not necessarily be actual captions in the channels.) The Elementary Video Stream indicates the stream’s starting and ending time codes.  You can compare these time codes to the captioning time codes by viewing the .scc file in a text editor.  The Starting Time Code should be on or before the first time code listed in the .scc file.

Information in the dialog box is also stored in the decode.log file:

caption analysis Pixeltools

 

View Captions

  1. Drop your file to be analyzed onto the “File to Decode or Analyze” edit box
  2. Depress the “de” speed button to open the Decode Window
  3. Select a menu item in the Decode Window Text Overlays | Closed Captioning | CEA-708
  4. Depress the View button (or depress the Step button to decode one frame at a time)

The video will be decoded and your selected captions will be displayed over the video in exact compliance with the CEA-608 and CEA-708 specifications.  Some popular video decoders do not follow the 608 or 708 specifications when displaying captions; they use their own format and style when rendering captions.

view captions Pixeltools

 

View Low Level Captioning Codes

  1. Drop your file to be analyzed onto the “File to Decode or Analyze” edit box
  2. Depress the St button to open the Statistics window
  3. Select the Statistics menu item View | Video Statistics | User Data
  4. Depress the View button (or depress the step button to decode each frame)

All user data detected in the file will be displayed in the Statistics window and in the decode.log file:

low level captioning Pixeltools

If no data appears in this window when running the decoder, there are no digital 608 and/or 708 captions in parts of the stream. If data appears, you can view the data to see if there are 608 and/or 708 captions in parts of the stream.

An example of a line of 608 and 708 captions can be interpreted as:

user data 608 and 708 compliance

Click on image to see larger view

Analyze CEA-708 Captions

  1. Drop your file to be analyzed onto the “File to Decode or Analyze” edit box
  2. Depress the St button to open the Statistics window
  3. Select the Statistics menu item View | Video Statistics | Digital Captioning | CEA-708 All Windows
  4. Depress the View button (or depress the step button to decode each frame)

analysis captions Pixeltools

The decoded 708 commands and text are displayed as they are decoded in the stream. This data is also saved in the decode.log file. You can view the different 708 service channels that are being utilized and see the text that is being presented in each of the services.

 

Analyze CEA-708 Captions Codes

  1. Drop your file to be analyzed onto the “File to Decode or Analyze” edit box
  2. Depress the St button to open the Statistics window
  3. Select the Statistics menu item View | Video Statistics | Digital Captioning | CEA-708 Raw Frames
  4. Depress the View button (or depress the step button to decode each frame):

decoding frame Pixeltools

The CEA-708 binary packets are displayed along with the Packet Size, Services, Data Bytes, and Sequence Incrementor.

 

Display CEA-608 Captions Text

  1. Drop your file to be analyzed onto the “File to Decode or Analyze” edit box
  2. Depress the St button to open the Statistics window
  3. Select the Statistics menu item View | Video Statistics | Digital Captioning | CEA Field 1 Windows
  4. Depress the View button (or depress the step button to decode each frame)

decoding closed captions Pixeltools

The CEA-608 text will be displayed as it is encountered frame by frame. Note that the text displayed is in Transmission order which may not be in Display order.

 

View Text in SCC file

  1. Drop your .scc file to be translated onto the “File to Decode or Analyze” edit box
  2. Depress the Update button

cea 608 frame code Pixeltools

The text and time code will be saved in a .txt file with the same name as the .scc file. Note that this file can be edited and the edited captions can be inserted in a MPEG file using Expert-Caption.

 

Extract Captions as .SCC file

  1. Drop your file to be processed onto the “File to Decode or Analyze” edit box
  2. Depress the Configure
  3. Check the Extract Streams | Save Digital Data Field1
  4. Enter the full path to the .scc file which will save the captions
  5. Close the dialog and depress the Update button

time code extraction Pixeltools

Captions detected in the stream will be saved in your selected .scc file.

 

Scrub Captions from MPEG file

  1. Drop your file to be scrubbed onto the “File to Decode or Analyze” edit box
  2. Depress the Configure
  3. Check the Fix Stream | Remove Existing Captioning
  4. Enter the name of your scrubbed file in the Save Fixed File edit box
  5. Uncheck the Add Closed Captions check box (if not adding captions at the same time)
  6. Close the dialog and depress the Update button.

scrab extractions Pixeltools

The captions will be removed and the resultant file saved as your desired fixed file.  Note that this option can be utilized in combination with closed captioning insertion.

 

Save Raw 708 Caption data from MPEG file

  1. Drop your file to be analyzed onto the “File to Decode or Analyze” edit box
  2. Depress the Configure
  3. Check the Extract Streams | Saved Closed Captioning
  4. Enter the full path for the file to contain the raw captions.  Filename must end with raw

raw file closed captioning Pixeltools

The raw file can be viewed with a text editor. (Add the .txt extension to the file name.)

raw captions Pixeltools

The raw file lists the decoded frame number and includes the packetization information in addition to the CEA-708 data.

 

Save All User Data into an Edit Decision List (EDL) file

  1. Drop your file to be processed onto the “File to Decode or Analyze” edit box
  2. Depress the Configure
  3. Check the Extract Streams | Saved Closed Captioning | Save Digital Data Field1
  4. Enter the full path for the file to contain the user data.  Filename must end with .edl
  5. Click Apply to close the dialog and depress the Update button on the main interface

edit closed captions Pixeltools

The resultant .edl file can be viewed in a text editor. The EDL file lists the Frame number. The next line contains the command HEXUSERDATA followed by the hex user data found in this frame.

save edited closed captions Pixeltools

This EDL file can be used to insert the user_data in another video file using any PixelTools video processing tool.

 

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