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Multi-language audio in Dolby E

GEP100 - HEP100

A description of how to encode multiple 3Gb/s, HD, SDin embedded domain Dolby E tothem PCM languages Dolby-E format and embed decoder with into a single SDIaudio videoshuffler stream A

A

®

® product application note

Quad speed

Upgradable to

3Gb/s Embedded

Metadata S2020

COPYRIGHT©2011 AXON DIGITAL DESIGN B.V. ALL RIGHTS RESERVED NO PART OF THIS DOCUMENT MAY BE REPRODUCED IN ANY FORM WITHOUT THE PERMISSION OF AXON DIGITAL DESIGN B.V.


EMBEDDED AUDIO AUDIO MULTI-LANGUAGE PROCESSING IN DOLBY-E

Introduction The use of Dolby-E encoding gives broadcasters and facility operators the ability to embed up to 64 audio channels into a single SDI video: 2 Dolby-E streams in each of the 4 audio groups with each stream having a maximum capacity of 8 mono audio channels. An example of the utilisation of this is where a broadcaster is producing a transmission feed mixed in 5.1 surround sound for reception in multiple territories, with each territory requiring their own local language. By encoding each surround and associated stereo mix in Dolby-E it is possible to include 8 languages in the SDI video which could then be passed through the playout path in the conventional manner.

The Dolby E signal is not intended for distribution usage; it is decoded back to baseband audio just prior to the final digital transmission, and then reencoded into the final audio format as required by the intended distribution platform. Possible Dolby E program configurations could include: ▪▪ 5.1 - 5 full range surround audio channels + a band limited low frequency effects channel ▪▪ 5.1+1+1 – 5.1 surround sound channels + 2 mono channels which could be used for audio description ▪▪ 5.1+2 – 5.1 surround sound channels + 1 stereo channel which might be used for an alternative two-track version of the surround sound mix

Alignment of Dolby-E in Video Systems Dolby E streams include audio and metadata encoded into blocks of SMPTE 337M data, streamed on a discrete AES/EBU channel or embedded into SDI. As the Dolby E bit-stream is normally carried along with video these data blocks are output at a rate associated with a chosen video frame rate. Possible video frame rates are: 29.97 fps (NTSC); 25 fps (PAL); 23.98, 24, 30 fps. The Dolby E specification also ensures that the audio frames are synchronous with video frames, enabling programmes to be switched and edited without having to decode and recode the audio. To allow error-free “cuts only” editing and video source switching in routers, mixers etc., a short period in each frame has silent samples around the point in the stream at which the edit or video switch is intended to occur, this period is known as the guard-band.

The point of where the guard band ends and the SMPTE 337M Dolby E data burst starts is often called the “Line Position.” This relates to a specific video line to which the start of the Dolby E data is aligned. The ideal location of a Dolby-E frame is so that it starts after the video switching point and it finishes before the end of the video frame. The location of the Line Position to place the Dolby-E frame in the centre of the video frame is 730µS after the start of the video frame, this can be safely varied by 680µS. The actual line that this timing is related to depends on the video standard being utilised: ▪▪ 625i25 (SD PAL) – Line 12 ▪▪ 720p50 (HD PAL) – Line 28 ▪▪ 1080i50 (HD PAL) – Line 21 ▪▪ 525i29.97 (SD NTSC) – Line 14 ▪▪ 720p59.94 (HD NTSC) – Line 32 ▪▪ 1080i59.94 (HD NTSC) – Line 26

Synapse Card Reference Selection and Video Timing The importance of correct system timing is critical in building a system that will successfully encode and embed Dolby-E within a SDI stream. The Dolby-E frames need to be generated at the same frame rate as the video they are to be embedded into and these frames need to be correctly aligned with the video frames. Synapse cards provide the necessary functionality and selection choices to allow this to reliably occur. The diagram below (page 6) shows a possible scenario where 8 separate surround sound sources are encoded and embedded into a single HD-SDI signal. In addition to embedding the Dolby streams

the HEB990 card also has a delay function which is used to synchronise the video with the Dolby encoded audio following the 1-frame processing delay. The diagram shows the DBE08 Dolby encoder cards connected to the embedder via an external AES connection and via the Synapse Add-On Bus which require the card encoder cards to be located immediately to right of the embedder in the same frame, this has the advantage that all of the connections are taken care of without external cables and also the various clocks on the Dolby encoder are locked to the video source via the

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EMBEDDED AUDIO AUDIO MULTI-LANGUAGE PROCESSING IN DOLBY-E MasterCard signal also carried on the bus. Up to four DBE08 cards can be connected in this manner each inserting the Dolby-E stream onto tracks 1/2 of successive SDI audio groups, these can then be repositioned onto the desired tracks in the output SDI stream using the audio shuffler functionality within the HEB990 embedder card. If locating the Dolby-E encoder card next to the embedder in not practicable, or there is a requirement for more than four Dolby-E streams, cards can be connected using external balanced or unbalanced AES cables, in which case the card should be locked to an external video reference signal synchronous with the video into which the Dolby-E encoded audio was to be embedded. The DBE08 Dolby-E encoder uses the reference signals distributed throughout the Synapse frame to determine where a Dolby frame should start and stop, therefore it is critical that the video into which the Dolby-E frames are to be embedded is referenced to the same source as the Synapse frame. The video should be timed so that it is

synchronous with the reference signal at the input of the HEB880 embedder, this can be achieved by adjusting the source’s timing or changing the amount of delay introduced into the video signal by the HEB990 embedder module. It should be noted that none of the cards in this system provide frame synchroniser functionality, if the source to the system is expected to change or its timing cannot be fixed and therefore changing its timing relationship with the Dolby-E encoder, Axon would recommend placing a synchroniser (such as the HFS010) in the video path before the de-embedder card. By adopting this methodology Dolby-E frames produced by the DBE08 card will be correctly inserted within the video frame on the embedder card. If further adjustment of the Dolby-E frame timing is found to be required it can be achieved using the Guard Band Delay control on the DBE08 card, this can add an additional 625-lines of delay to the Dolby-E frames.

Card Settings The following tables give examples of the configuration options required to successfully decode the Dolby-E stream, insert a V/O into it, encode the mix as a Dolby-E stream and embed the stream into the original SDI signal. Please note that the cards have considerably more settings than shown here and these should be set to match the user’s individual requirements.

DBE08 Settings (Connection via Synapse Add-on Bus) 1. Lock Mode = MasterCard, references the encoding processes to the HEB880 MasterCard’s clocks. The framing of Dolby-E packets is related to the Ref1 video timing. 2. Lock Mode = Reference, locks the cards time and Dolby-E packet phasing to external reference Ref1 3. Program Config should be configured to suit the user’s requirements (shown here for 5.1 surround sound). The letter refers to the Metadata configuration chosen (see item 4). 4. Bypass Delay = 40mS, if the Dolby-E encoder is bypassed this configuration delays the audio by the same amount as the encoding process to ensure continued lip-sync. 5. Selects the Metadata set to be edited, Sets are used by the Program Config (see item 2). 6. Audio Coding Mode = 3/2 and LFE Enable = , configures the encoding format in the metadata used by subsequent decoders, this example it configured for 5.1.

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EMBEDDED AUDIO AUDIO MULTI-LANGUAGE PROCESSING IN DOLBY-E HEB990 Settings 1. Input Select = SDI-1 & Switch Back = Off selects SDI 1 as the source of video to have the Dolby-E streams added to and also prevents the module switching to the other source should the input fail. Lock Mode = Ref1 locks the card to an external source of video reference, essential if the Dolby-E encoding and insertion timing is to be correct 2. Frame Delay = 1 Frame, adds delay to the video signal to compensation for the Dolby-E processing time. 3. Non PCM Bypass = On, this bypasses audio processing for signals which are not PCM audio, such as a Dolby-E encoded data stream. 4. SRC Local xx/x = Transparent, ensures Dolby-E signals will not be processed, this is simply a fail-safe, 3 (above) accomplishes the same thing.

1. Add On A = Selected, the configuration shown will route the audio from the Add-On bus (originating on the DBE08 card) to the SDI Group 1, channels 1 and 2, inserting Dolby-E encoded audio onto tracks 1 and 2 in the SDI stream. Note the channels need to be selected individually. 2. Local A = Selected, routes the Dolby-E stream from AES-1 to channels 1 and 2 of audio group 3 (SDI tracks 9 and 10).

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EMBEDDED AUDIO AUDIO MULTI-LANGUAGE PROCESSING IN DOLBY-E

Dolby-E line position alignment process ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪ ▪▪

Connect cards as shown below ensuring the Synapse frames have at least one external reference connected and that they are all originate from the same generator. Determine if the timing of the input video may change – if yes install frame synchroniser prior to embedder. Set the HEB990 Lock-Mode to the reference bus which has an external reference connected i.e. Lock Mode = Ref1. Ensure the Ref-Input of the DBE08 Dolby-E encoders is set to the same reference source. Set the delay of the HEB990 to 1 Frame to compensate for the processing delay through the Dolby-E encoders. Adjust the timing of the video source to the HEB990 embedder to be synchronous with the frame’s internal reference at the output of the card (this can be easily ascertained using the Measurement option on a Tektronix 7120 WFM or similar). Timing adjustments can be made at the source of the video prior to the embedder or using the delay functionality of the embedder card. This will align the video with the Dolby-e data packets being generated by the DBE08 cards. If the DBE08 is connected to the embedder by the Synapse Bus select Lock Mode = MasterCard, otherwise select Reference. Check the positioning of the Dolby-E data within the video output from the HEB990, either change the card’s delay so that the Line Position is correct or use the Guard-Band Shift function on the DBE08 card to delay the Dolby frames if required.

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Language F – SL/SR

Language F – C/LFE

Language F - L/R

Language E – SL/SR

Language E – C/LFE

Language E - L/R

1

2

3

4

1

DOLBY E OUTPUT

Language B - L/R

Language A – SL/SR AES 7/8

AES 5/6

1

2

1

2

3

4

INTERNAL SYNAPSE BUS

Audio in/outputs To/from Synapse bus

PLL

3

2

BY-PASS DELAY

DARS GENERATOR

ENCODER

1

µP

Rack controller

+

CHANNEL 3/4 [AUX] SELECTION

AES/EBU FORMAT

AUX OUT

Language B – SL/SR

Language B – C/LFE

AES 7/8

AES 5/6

AES 3/4

AES 1/2

METADATA

GENERATOR

GAIN CONTROL

CHANNEL SWAP

AES/EBU FORMAT

MAIN OUTPUT SELECTION

Rack controller

AUX OUT

AES 3/4

METADATA

DELAY

DELAY

DELAY

DELAY

2

µP

+

CHANNEL 3/4 [AUX] SELECTION

AES/EBU FORMAT

Language A – C/LFE

Language A - L/R

GPI

SRC

SRC

SRC

SRC

INTERNAL SYNAPSE BUS

3

BY-PASS DELAY

DARS GENERATOR

ENCODER

DOLBY E OUTPUT

GPI

AES 7/8

AES 5/6

AES 3/4

AES 1/2

DBE08

2

Audio in/outputs To/from Synapse bus

PLL

GENERATOR

GAIN CONTROL

CHANNEL SWAP

AES/EBU FORMAT

METADATA

DELAY

DELAY

DELAY

DELAY

AES 1/2

GPI

SRC

SRC

SRC

SRC

MAIN OUTPUT SELECTION

G/HEB990 ONLY

AES/EBU INPUT 8

AES/EBU INPUT 7

AES/EBU INPUT 6

AES/EBU INPUT 5

AES/EBU INPUT 4

AES/EBU INPUT 3

AES/EBU INPUT 2

AES/EBU INPUT 1

METADATA

3Gb/s, HD, SD IN 2

3Gb/s, HD, SD IN 1

METADATA

1

DBE08

Up to 4 AES streams each carrying a Dolby-E encoded language

Input Program Video

GPI

AES 7/8

AES 5/6

AES 3/4

AES 1/2

System Schematic

MULTI-LANGUAGE AUDIO IN DOLBY-E

SRC

SRC

SRC

SRC

SRC

SRC

SRC

SRC

1

1

DBE08

1

DBE08

Eq

Eq

2

SRC

SRC

SRC

SRC

2

SRC

SRC

SRC

SRC

ADJUSTABLE OFFSET DELAY 0-500ms

GENERATOR

GAIN CONTROL

CHANNEL SWAP

1

GENERATOR

GAIN CONTROL

CHANNEL SWAP

1

2

3

4

2

3

4

2

2

1

1

EMB B

µP

RACK CONTROLLER

Rack controller

µP

Rack controller

+

CHANNEL 3/4 [AUX] SELECTION

AES/EBU FORMAT

AES/EBU FORMAT

MAIN OUTPUT SELECTION

µP

+

CHANNEL 3/4 [AUX] SELECTION

AES/EBU FORMAT

AES/EBU FORMAT

MAIN OUTPUT SELECTION

EMB D

A

B

AUX OUT

DOLBY E OUTPUT

AUX OUT

DOLBY E OUTPUT

GPI/O

3Gb/s, HD, SD OUT 2

3Gb/s, HD, SD OUT 1

2 Additional DBE08 modules can be connected on the Add-On bus

3

BY-PASS DELAY

DARS GENERATOR

ENCODER

3

BY-PASS DELAY

DARS GENERATOR

ENCODER

INTERNAL SYNAPSE BUS

1

EMB C

AUDIO INPUTS FROM SYNAPSE BUS 4

INTERNAL SYNAPSE BUS

Audio in/outputs To/from Synapse bus

PLL

DELAY

DELAY

DELAY

DELAY

3

INTERNAL SYNAPSE BUS

2

4 Ch

4 Ch

4 Ch

B

A

EMB A

A = SINGLE CHANNEL B = DUAL CHANNEL

4 Ch

A

B

4 Ch 4 Ch 4 Ch 4 Ch

PRESET BASED 32X16 CHANNEL (24X16 FOR G/HEB900) INPUT MULTIPLEXER FOR EVERY EMBEDDER GROUP

B

A

S2020 INSERTION

ADJUSTABLE OFFSET DELAY 0-500ms

Audio in/outputs To/from Synapse bus

PLL

DELAY

DELAY

DELAY

DELAY

REFERENCE INPUTS 2

DELAY GAIN/PHASE

DELAY GAIN/PHASE

DELAY GAIN/PHASE

DELAY GAIN/PHASE

DELAY GAIN/PHASE

DELAY GAIN/PHASE

DELAY GAIN/PHASE

PLL

AUTO MUX

2x1 OR 2x2

DELAY GAIN/PHASE

AUTO PHASER

AUTO PHASER

GEB990 – GEB900 – HEB990 – HEB900

Delay = 1Frame to compensate for Dolby-E processing latancy

Up to 4 AddOn buses each carrying a Dolby-E encoded language

Output Video with up to 8 Dolby-E encoded audio languages

AN2011-06 Multi-language audio in Dolby-E.pdf  
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