Transmission and transcoding of subtitles is typically handled by taking the subtitles from the SDI or TS video feed and converting them to the different transmission formats depending on the distribution technology and local standards, e.g. traditional terrestrial, DTH broadcast or OTT. The most common transcoding application is in the last part of the distributions stage, i.e. the headend, where EBU teletext is transcoded to DVB bitmaps.
Transcoding from image-based DVB subtitling to text-based DVB teletext requires Cavena OCR transcoding, which is one of the capabilities of the Subtitle Transmission Unit (STU). By using one or several such OCR engines in parallel with dynamic image processing, the image-based subtitles are converted to text-based subtitles including an accurate time code in less than half a second . This can be compared to the 3-5 seconds that is the time it typically takes to do the video encoding, which is done in parallel to the subtitle transcoding.
As DVB teletext is defined as EBU teletext in a Transport Stream (TS) it cannot manage Asian character sets natively. However, in the Cavena-based subtitle encoding and transcoding solution, DVB teletext does support Asian characters thanks to the use of the Cavena P31 format.
DVB teletext is the standard input to many OTT platforms and can be converted to a range of formats and adjusted for multiple screen sizes and devices. Read more about the Cavena-based solution for OCR Subtitling for OTT distribution.
WHAT IT DOES
- Transcodes subtitle data from one format to another.
- Supports a wide range of SDI input formats: EBU TELETEXT (SD), OP-47/SMPTE 2031 (HD), EIA 608/708, Cavena format (P31).
- Supports a wide range of SDI output formats: EBU TELETEXT (SD), OP-47/SMPTE 2031 (HD), EIA 608/708, Cavena format (P31), SD/HD In-vision
- Supports a wide range of TS input formats: DVB Teletext, DVB Subtitling, EIA 608/708, ARIB, Cavena format (P31).
- Supports a wide range of TS output, DVB Teletext, DVB Subtitling, EIA 608/708, ARIB, Cavena format (P31), SCTE-27.
- Supports a wide range of Asian languages with Cavena P31.
HOW IT WORKS
- The Subtitles are retrieved from an SDI input or from a Transport Stream (TS) in various different formats, see image to the left
- The Subtitles are transcoded to the output format requested using the Subtitle Transmission Unit (STU)
- Input and output formats are independent of each other
HOW TO DEPLOY
Edgeware’s Cavena-based subtitle encoding and transcoding software runs on Windows and a standard server, and is quick to deploy. The solution is standalone and requires no integration to automation or similar control system.