[FFmpeg-devel] Captions SCC

[Tom Vaughan]

Soft Works said... "the CC data needs to get into the video frames - so that it exists as input to the video encoder.
For the same reason, it is also not possible to add CCs at the muxer level. It always requires video encoding because the data needs to get into the video stream itself, so there's no way to get data from an SCC file into a video stream currently."

You're confusing subtitles with closed captions. Subtitles are text that is composited into the video. CEA-708 closed captions are carried as metadata in SEI NAL units, muxed into the elementary video stream.

Tom

On 2/6/25, 11:48 PM, "ffmpeg-devel on behalf of Soft Works" <ffmpeg-devel-bounces at ffmpeg.org <mailto:ffmpeg-devel-bounces at ffmpeg.org> on behalf of softworkz-at-hotmail.com at ffmpeg.org <mailto:softworkz-at-hotmail.com at ffmpeg.org>> wrote:


> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org <mailto:ffmpeg-devel-bounces at ffmpeg.org>> On Behalf Of
> Devlist Archive
> Sent: Friday, February 7, 2025 6:13 AM
> To: FFmpeg development discussions and patches <ffmpeg-
> devel at ffmpeg.org <mailto:devel at ffmpeg.org>>
> Subject: Re: [FFmpeg-devel] Captions SCC
> 
Hi Zack,
that message from "Jack" had confused me for a moment, but on re-reading it appears to be an AI response.
The content is total nonsense. There is no "SCC" encoder in ffmpeg, and if there was one, it wouldn't help much because the CC data needs to get into the video frames - so that it exists as input to the video encoder.
For the same reason, it is also not possible to add CCs at the muxer level. It always requires video encoding because the data needs to get into the video stream itself, so there's no way to get data from an SCC file into a video stream currently.

The only way in the ffmpeg architecture to get CC data encoded would be at the filtering level. The Subtitle Filtering patchset that I have submitted a while ago has a "splitcc" filter which has video as input and a video plus a subtitle pin/pad at the output side.
What would be needed is a reverse pendant like a "mergecc" filter with video and subtitles input - plus a CEA-608/708 encoder.

softworkz