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Content for  TS 26.114  Word version:  18.6.0

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Q  Computation of b=AS for EVS |R12|p. 412

Q.1  Generalp. 412

This Annex contains examples of computing b=AS for EVS Primary mode when ptime=20, and ptime=40. In these examples, it is assumed that no extra bandwidth is allocated for redundancy.

Q.2  Procedure for computing the bandwidthp. 412

The bandwidth is calculated using the following procedure when no extra bandwidth is allocated for redundancy:
  1. Calculate the size of the RTP payload, see below.
  2. Calculate the size of the IP packets by taking the RTP payload size (in bytes) and adding the IP/UDP/RTP overhead: 20 bytes for IPv4; 40 bytes for IPv6; 8 bytes for UDP; 12 bytes for RTP.
  3. Convert the IP packet size to bits.
  4. Calculate the required bit-rate (bps) given the packet size and the packet rate: 50 packets per second for 1 frame per packet; 25 packets per second for 2 frames per packet.
  5. The b=AS bandwidth is then calculated by converting the required bit-rate to kbps and rounding to the nearest higher integer value.
If the SDP includes multiple codecs and/or configurations, the bandwidth is calculated for each configuration and the b=AS bandwidth is set to the highest of the bandwidths.
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Q.3  Computation of RTP payload sizep. 412

When the b=AS bandwidth is computed, it is assumed that the codec is using the highest allowed bit-rate for each frame.
The RTP payload size for the 2 bytes header-full payload format and 1 frame/packet is calculated from the following components:
  • 8 bits for the codec mode request (CMR)
  • 8 bits for the table of content (ToC)
  • N bits for the speech frame (size depends on bit-rate)
  • No padding in the end of the RTP payload is needed since each item is already an integer number of octets
The RTP payload size for the 2 bytes header-full payload format and 2 frames/packet is calculated from the following components:
  • 8 bits for the codec mode request (CMR)
  • 16 bits for the table of content (ToC)
  • N bits for the speech frame (size depends on bit-rate)
  • No padding in the end of the RTP payload is needed since each item is already an integer number of octets
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Q.4  Detailed computationp. 413

The Tables below give a detailed description of the bandwidth computation. The b=AS bandwidth is not defined for SID.
For each codec mode, b=AS value of EVS AMR-WB IO mode is the same as the b=AS value of AMR-WB in octet-aligned mode. See clause K.4.
Mode 7.2 8 9.6 13.2 16.4 24.4 32 48 64 96 128 SID
Bits per speech frame14416019226432848864096012801920256048
Speech frame size (bytes)192024334161801201602403206
CMR and ToC (bits)161616161616161616161616
RTP payload (bits)16817620828034450465697612961936257664
RTP header (bits)969696969696969696969696
UDP header (bits)646464646464646464646464
IPv4 header (bits)160160160160160160160160160160160160
Total bits per 20 ms4884965286006648249761296161622562896384
Total bit-rate (kbps)24.424.826.43033.241.248.864.880.8112.8144.819.2
AS (kbps)252527303442496581113145N/A
Mode 7.2 8 9.6 13.2 16.4 24.4 32 48 64 96 128 SID
Bits per speech frame14416019226432848864096012801920256048
Speech frame size (bytes)192024334161801201602403206
CMR and ToC (bits)161616161616161616161616
RTP payload (bits)16817620828034450465697612961936257664
RTP header (bits)969696969696969696969696
UDP header (bits)646464646464646464646464
IPv6 header (bits)320320320320320320320320320320320320
Total bits per 20 ms64865668876082498411361456177624163056544
Total bit-rate (kbps)32.432.834.43841.249.256.872.888.8120.8152.827.2
AS (kbps)333335384250577389121153N/A
Mode 7.2 8 9.6 13.2 16.4 24.4 32 48 64 96 128
Bits per speech frame144160192264328488640960128019202560
Speech frame size (bytes)18202433416180120160240320
CMR and ToC (bits)2424242424242424242424
RTP payload (bits)312344408552680100013041944258438645144
RTP header (bits)9696969696969696969696
UDP header (bits)6464646464646464646464
IPv4 header (bits)160160160160160160160160160160160
Total bits per 40 ms6326647288721000132016242264290441845464
Total bit-rate (kbps)15.816.618.221.8253340.656.672.6104.6136.6
AS (kbps)161719222533415773105137
Mode 7.2 8 9.6 13.2 16.4 24.4 32 48 64 96 128
Bits per speech frame144160192264328488640960128019202560
Speech frame size (bytes)18202433416180120160240320
CMR and ToC (bits)2424242424242424242424
RTP payload (bits)312344408552680100013041944258438645144
RTP header (bits)9696969696969696969696
UDP header (bits)6464646464646464646464
IPv6 header (bits)320320320320320320320320320320320
Total bits per 40 ms79282488810321160148017842424306443445624
Total bit-rate (kbps)19.820.622.225.8293744.660.676.6108.6140.6
AS (kbps)202123262937456177109141
Mode 7.2 8 9.6 13.2 16.4 24.4 32 48 64 96 128
Bits per speech frame144160192264328488640960128019202560
Speech frame size (bytes)18202433416180120160240320
CMR and ToC (bits)2424242424242424242424
RTP payload (bits)312344408552680100013041944258438645144
RTP header (bits)9696969696969696969696
UDP header (bits)6464646464646464646464
IPv4 header (bits)160160160160160160160160160160160
Total bits per 20 ms6326647288721000132016242264290441845464
Total bit-rate (kbps)31.633.236.443.6506681.2113.2145.2209.2273.2
AS (kbps)32343744506682114146210274
Mode 7.2 8 9.6 13.2 16.4 24.4 32 48 64 96 128
Bits per speech frame144160192264328488640960128019202560
Speech frame size (bytes)18202433416180120160240320
CMR and ToC (bits)2424242424242424242424
RTP payload (bits)312344408552680100013041944258438645144
RTP header (bits)9696969696969696969696
UDP header (bits)6464646464646464646464
IPv6 header (bits)320320320320320320320320320320320
Total bits per 20 ms79282488810321160148017842424306443445624
Total bit-rate (kbps)39.641.244.451.6587489.2121.2153.2217.2281.2
AS (kbps)40424552587490122154218282
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