Ultra-High Definition (UHD) programmes are not accepted by SVT.
The quality of the link from the remote location to SVT’s point of delivery has a major effect on the quality of the programme seen by the audience. The content, genre and workflow requirements of the programme are the primary factors that determine the bandwidth of the link.
For instance, programmes that feed into post production via the link will usually require a higher link specification than programmes that are completed on site, where the link is only used for transmission. The same can apply to programmes that are archived via a link.
Link specifications are always a trade-off between quality, cost and available bandwidth. However, the link should never be considered in isolation. In addition to the type and settings of the link encoder, the use of location radio cameras, and the transmission compression used by SVT, must be considered. Where there is any doubt, programme production companies should ask their link provider to speak to SVT’s technical contacts.
In all instances, the delivered picture format shall be:
- With 50 Hz motion portrayal, preferably:
- 1280 pixels wide x 720 pixels high;
- 16:9 Aspect Ratio, Full Frame (no Letterboxing/Pillar-boxing);
- 50 frames per second, delivered as 50 progressive frames per second.
- Or, still with 50 Hz motion portrayal, optionally:
- 1920 pixels wide x 1080 pixels high;
- 16:9 Aspect ratio, Full Frame (no Letterboxing/Pillar-boxing);
- 25 frames per second, delivered as 50 interlaced fields per second.
The target quality level of compressed programme material is divided into three categories:
- Grade A – Programme material of prime events like concerts, demanding sports and other events where high quality is important – i.e. the main quality target, in line with internationally accepted contribution quality.
- Grade B (SVT specific) – When it is judged that some quality may be sacrificed due to technical or economic reasons.
- Grade C (SVT specific) – For programme material that will not be post-processed and where the content motivates that some quality loss may be acceptable due to technical limitations.
Contribution of programmes in Standard Definition quality (legacy equipment) is described SD Links (if required).
Any external reference source at the remote site should be locked to GPS.
Latency of the programme feed must be less than 5 seconds, unless required by exceptional technical considerations.
The types of links used for any Live HD programmes shall fall into the following categories:
Uncompressed via Optical Fibre
- 1.485 Gbps HD-SDI connection, SMPTE 292M, (often known as 1.5 Gbps HD-SDI). This remains uncompressed along its route to the point of delivery.
- Wherever possible, practical, or cost-effective, programmes should use an uncompressed 1.485 Gbps HD-SDI connection.
- In all instances where the signal can be carried uncompressed, multichannel and/or stereo audio for the programme should be carried as discrete linear PCM (unless ‘Dolby E’ is requested by SVT).
- Uncompressed contribution links fall under category Grade A.
Compressed via Optical Fibre
- Links that provide a 1.485 Gbps HD-SDI connection at the point of delivery, but which use compression/decompression along their route.
- Locations with optical Ethernet access should use compression encoders and decoders that allow HD-SDI to be transferred with 10-bit JPEG2000 compression over IP-protocol using MXF encapsulation of compressed data. The circuit must be single-hop or managed to guarantee the necessary quality of service.
Single-hop Fibre Connections: Compression Codecs Diagram
Compressed via Satellite Link
Where fibre is not available, links via satellite may be used. The following are permissible and achievable largely by using DVBS2 modulation schemes. Modulation schemes should be carefully chosen so that the increase in transponder capacity (in MHz) required to deliver the optimal video bitrate (in Mbps) does not come at the cost of a decreased robustness of signal.
Single-hop Satellite Links: Nominal Video Bitrate Diagram
Compressed via Microwave Point-to-Point Link
In some locations a point-to-point microwave link may be used as an alternative to satellite links. Microwave links can be used for short hops from the location to a fixed fibre link point or where a satellite up-link has to be remote from the production location. Where microwave links are used to feed a second compressed link, the signal should not be decoded back to baseband but passed to the second link as a transport stream.
Compressed via Microwave Point-to-Point Link: nominal Bitrate Diagram
SD Links (if required)
Where Compressed Standard Definition contribution is used, it should be compressed using MPEG-4 or MPEG-2 Long GOP. The GOP structure and encoder setup are the same as the HD requirements in Codec Requirements, SD and HD programmes. The payload on the link should have a nominal video bitrate of:
SD Links (if required) Diagram
In all instances where the signal can be carried uncompressed, stereo audio for the programme should be carried as discrete linear PCM. If the signal must be carried in a compressed format, Stereo audio should be carried as MPEG-1 Layer II (stereo) at 384 kbps.
Multichannel audio (surround sound) should normally be discrete PCM where there is sufficient bandwidth available in the link to the point of delivery.
Dolby E should be used for multi-channel audio when bandwidth is limited or at the request of SVT. Settings for Dolby E encoding are in Appendix C.
Use of the Low Frequency Effect Channel (LFE) channel is optional. Use of the LFE channel should comply with ITU-R BS.775. There should be no sample timing differences between the individual channels of a surround signal.
Each stereo pair or multi-channel group (the 6 audio tracks of a surround sound signal) must be transported in a single SMPTE ST.302 PES to maintain the phase relationship between channels.
Some encoder/decoder hardware support phase coherence between MPEG-1 Layer II audio pairs that together form a carrier of multichannel audio. If used, care must be taken to ensure that the phase coherence is preserved. Audio metadata is not carried in such streams and must therefore be supplied by other means, see Dolby Metadata Settings in Audio Technical Requirements.
Audio Track Allocation
It is difficult to prescribe the exact audio track layout for all live programmes. International, host broadcaster, local requirements and link bandwidth may vary the audio layout requirements.
SVT and other broadcasters (e.g. all broadcasters in the UK) are working towards the standard audio layout below. However, in many situations this layout is not yet implemented due to legacy requirements – see Appendix B regarding SVT’s current audio track allocation.
Audio Track Allocation Diagram
Audio - continued
Commentary Lazy Talkback
Spill of crowd or general background noise picked up by the commentary microphones contribute acoustically to the width of the front image.
In sports coverage (and other programmes produced in very noisy locations) it is important to ensure that there is some residual crowd sound in the centre channel, to minimise the audible ‘hole’ that otherwise results when a commentary microphone is muted, for example by the activation of ‘Lazy Talkback’.
Radio link cameras are always a compromise between delay and image quality. Image quality should always be the overriding consideration. Where radio and cabled cameras are mixed covering a location with lip-sync, and it is not possible to delay the audio, the radio camera should not have a delay greater than 40 ms compared to the cable cameras. The director is responsible for making sure any visible lip-sync issues are kept to a minimum.
Where all cameras use radio links, the audio must be delayed matching the video. To minimise the issues caused by open talkback, and presenter switched talkback, the AV sync can be ±20 ms.
Programmes should use local time of day timecode pertinent to the venue and this should be carried in the VANC unless requested otherwise by SVT.
Ancillary Data (VANC)
Codec Requirements, SD and HD programmes
MPEG-2 Encoders – additional requirements
- GOP (Group-of-Pictures) should be 30 frames (50p) and 15 frames (25i). This represents a good balance between coding efficiency (requiring long GOPs) and error resilience (requiring short GOPs).
- B-frames should not be used as these are typically coded at a lower quality than I and P frames and will lead to poor picture quality in the home. Note: not all encoders on the market allow B-Frames to be disabled, so please check before accepting the unit.
- GOP structure should be /IPPPPPPPPPPPPPPPPPPPPPPPPPPPPP/ (50p) and /IPPPPPPPPPPPPPP/ (25i).
- 4:2:2 colour subsampling should be used to avoid colour smearing when concatenated with the 4:2:0 emission coders used for broadcast transmission.
- “Intra-DC precision” should be set to 11 bits. 11 bits are required in the DCT (Discrete Cosine Transform) domain in order to accurately convey an 8-bit video signal. This is not normally a user setting but should be checked with an analyser before accepting the encoder.
H.264 Encoders – additional requirements
- 10-bit video is preferred. There is no bitrate penalty.
- GOP length should be 30 frames (50p) and 15 frames (25i), in line with MPEG-2.
- B-frames and hierarchical B-frames are permitted.
- 4:2:2 colour subsampling is preferred, but 4:2:0 may be acceptable.
H.265 (HEVC) Encoders
- Use of HEVC/H.265 must be discussed and approved by SVT in advance.