What are VBI and VANC?
VBI (Vertical Blanking Interval) and VANC (Vertical Ancillary Data) are data areas able to carry captioning information, subtitles are embedded in whether VBI or VANC depending on whether video is analog or digital:
ANALOG TV - In analog television, closed captioning is carried out according to whether the signal is NTSC or PAL:
NTSC - In NTSC systems, captions are carried out in the VBI line 21 using the CEA-608 standard in the field 1 (cc1,cc2,t1,t2) and field 2 (cc3,cc4,t2,t4).
PAL - In PAL systems, captions are carried out in the VBI line 16 using the VPS Telext standard.
DIGITAL TV - In digital television, closed captioning is carried out according to whether the signal is SD or HD:
SDTV - In SD digital television (i.e. HD-SDI), closed captioning is carried out in the VBI line 21 using the CEA-608 standard in the field 1 (cc1,cc2,t1,t2) and field 2 (cc3,cc4,t2,t4). For some SD formats, closed captioning can be carried out in the VANC line 9 (most typically used) into multiple language-specific service captions (cs1, cs2...) using the CEA-708 standard.
HDTV - In HD digital television (i.e. HD-SDI), closed captioning is carried out in the VANC line 9 (most typically used) into multiple language-specific service captions (cs1, cs2...) using either the CEA-708 standard (compatible with the CEA-608 standard).
NB: Refer to "RZCP Transcoder workflows" and "Flexy Converter workflows"chapters for Information on how to handle VBI/VANC subtitles via T-workflow.
Which codecs support VBI and VANC?
In order to embed VBI and VANC data, the target video format must support VBI/VANC data preservation for storing captions either frame-based (into video frames) or track-based (into file container). Listed below are detailed the storage media types that support VANC and VBI:
VBI & VANC PRESERVATION CODECS
Track-based (in metadata) :
VBI
Codec - MPEG-2 SD
Frame-based (in video essence) : Yes
Track-based (in metadata) : ▪Omneon QT VBI file (MOV)
▪VBI track (GXF)
Codec - DV, DVCPRO, DVCPRO 50
Frame-based (in video essence) : No
Track-based (in metadata) : ▪SMPTE 436M (MXF)
▪VBI track (GXF)
VANC
Codec - MPEG-2 SD/HD
Frame-based (in video essence) : Yes
Track-based (in metadata) : ▪SMPTE 436M (MXF)
▪VANC track (GXF)
Codec - DVCPRO HD
Frame-based (in video essence) : Yes
Track-based (in metadata) : ▪SMPTE 436M (MXF)
▪VANC track (GXF)
Codec - AVC-Intra class 50/100
Frame-based (in video essence) : Yes
Track-based (in metadata) : ▪SMPTE 436M (MXF)
▪VANC track (GXF)
Codec - DNxHD
Frame-based (in video essence) : Yes
(Avid's proprietary format)
Track-based (in metadata) : ▪SMPTE 436M (MXF)
▪QT CC track (MOV)
Codec - ProRes/ProRes HQ
Frame-based (in video essence) : Yes
(Apple's proprietary format)
Track-based (in metadata) : ▪SMPTE 436M (MXF)
▪QT CC track (MOV)