Line 21 VBI captioning is indeed the standard for standard definition, baseband digital and analog video. It's also and the standard for some interchange formats like D10 / IMX, both of which use MPEG-2's 4:2:2 profile to encode a 720x512 image for NTSC, which includes all VBI data (CC and VITC etc).
However, in the compressed domain, an end user would be unlikely to see captions in this form. Quite frequently the 608 (or 708) data packets are stored in the MPEG-2 user data, or as H.264 SEI messages. ATSC A/53 defines both methods.
As an aside, things are a bit different in the HD world. Baseband HD video is usually transported over HD-SDI. In this scenario, captions and other metadata are stored in the vertical ancillary (VANC) data. This VANC data can be partially (or sometimes completely) retained when capturing baseband HD-SDI into a file. However, it's more common for captions to instead be extracted from the VANC, and inserted into MPEG-2 user data, H.264 SEI messages, or a standalone caption file during capture.
Most of that is fairly off-topic, but I find captions interesting (and endlessly frustrating).
Derek
However, in the compressed domain, an end user would be unlikely to see captions in this form. Quite frequently the 608 (or 708) data packets are stored in the MPEG-2 user data, or as H.264 SEI messages. ATSC A/53 defines both methods.
As an aside, things are a bit different in the HD world. Baseband HD video is usually transported over HD-SDI. In this scenario, captions and other metadata are stored in the vertical ancillary (VANC) data. This VANC data can be partially (or sometimes completely) retained when capturing baseband HD-SDI into a file. However, it's more common for captions to instead be extracted from the VANC, and inserted into MPEG-2 user data, H.264 SEI messages, or a standalone caption file during capture.
Most of that is fairly off-topic, but I find captions interesting (and endlessly frustrating).
Derek
Castle clash best hero for war god. We need to be able to pass EIA-608 closed captions through the card, into an SDI to Analog mini converter and finally into a TV via the AV video port. In an attempt to understand the decklink SDK and EIA-608 closed captions I changed the code in the VancOutput.cpp. EIA-608, also known as 'line 21 captions' and 'CEA-608', was once the standard for closed captioning for NTSC TV broadcasts in the United States, Canada and Mexico. It also specifies an 'Extended Data Service', which is a means for including a VCR control service with an electronic program guide for NTSC transmissions that operates on the even line 21 field, similar to the TeleText based VPS.
#1482openenhancement
| Reported by: | Owned by: | ||
|---|---|---|---|
| Priority: | wish | Component: | avformat |
| Version: | git-master | Keywords: | |
| Cc: | Blocked By: | ||
| Blocking: | Reproduced by developer: | no | |
| Analyzed by developer: | no |
Description
Attachments (1)
- sub.srt (113.2 KB) - added by ramitbhalla8 years ago.
Download all attachments as: .zip
Change History (31)
Changed 8 years ago by ramitbhalla
- Attachmentsub.srt added
comment:2follow-up:↓ 3 Changed 8 years ago by ramitbhalla
comment:3 in reply to: ↑ 2 Changed 8 years ago by Cigaes
comment:4follow-up:↓ 5 Changed 8 years ago by ramitbhalla
Description
Attachments (1)
- sub.srt (113.2 KB) - added by ramitbhalla8 years ago.
Download all attachments as: .zip
Change History (31)
Changed 8 years ago by ramitbhalla
- Attachmentsub.srt added
comment:2follow-up:↓ 3 Changed 8 years ago by ramitbhalla
comment:3 in reply to: ↑ 2 Changed 8 years ago by Cigaes
comment:4follow-up:↓ 5 Changed 8 years ago by ramitbhalla
comment:5 in reply to: ↑ 4 Changed 8 years ago by cehoyos
comment:7 Changed 8 years ago by ramitbhalla
comment:9 Changed 8 years ago by Cigaes
comment:11follow-up:↓ 12 Changed 8 years ago by pross
comment:12 in reply to: ↑ 11 Changed 8 years ago by cehoyos
- Keywordscc added
- Version changed from unspecified to git-master
comment:14 Changed 8 years ago by reimar
comment:16 Changed 8 years ago by reimar
comment:18 Changed 8 years ago by reimar
comment:20 Changed 8 years ago by cehoyos
comment:21 Changed 8 years ago by pross
Last edited 8 years ago by pross (previous) (diff)
comment:23 Changed 8 years ago by reimar
comment:25 Changed 8 years ago by reimar
Extract Eia 608 Captions Ffmpeg File
comment:27 Changed 7 years ago by ramitbhalla
comment:28 Changed 7 years ago by cehoyos
- Component changed from undetermined to avformat
- Keywordswtv added
- Priority changed from normal to wish
- Status changed from new to open
- Summary changed from FFMPEG fails to create a SRT file when extracting Subtitles to Support eia_608 in wtv
- Type changed from defect to enhancement
comment:29 Changed 5 years ago by cehoyos
- Ccer.anshul.maheshwari@gmail.com added
Eia 608 Standard
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