le (MP) level 3.1 main tier. 5.3.2.1. H.264 codec H.264 profile is identified by the parameter profile-level-id - in the SDP offer. The maximum image size (number of pixels) and the maximum number of frames per second for the CBP profile level 1.2 can take several values: - size 176 X 144, 60.6 frame/s; - size 320 X 240, 20 frame/s; - size 352 X 288, 15.2 frame/s. Several actual sizes of the image can be negotiated and are identified by the parameter a = imageattr in the SDP offer. The maximum rate supported by the profile is equal to 384 kbps. The reserved actual reserved is indicated by the parameter b = AS in the SDP offer. m=video 49154 RTP/AVP 99 b=AS: 315 a=rtpmap : 99 H264/90000 a=fmtp 99 profile-level-id=42e00d a=imageattr:! send [x=176, y=144] [x=224,y=176] [x=272,y=224] [x=320,y=240] recv (x=176,y=144] [x=224, y=176] [x=272,y=224] [x=320,y=240] 172 VoLTE and ViLTE 5.3.2.2. H.265 codec The H.265 codec presents the following improvements compared to H.264 codec: - for the same quality, the rate is decreased; - for an equivalent rate, the quality is improved. The maximum image size (number of pixels) and the maximum number of frames per second for the MP profile level 3.1 main tier can take several values: - size 720 x 576, 75 frame/s; - size 960 x 540, 60 frame/s; - size 1280 x 720,33.7frame/s. In the following example, the mobile is equipped with a 5-inch screen which supports an 848 X 480 frame size and 25 frames per second. The SDP offer provides H.265 codec, H.264 level 3.1 for the frame size 848 X 480 and H.264 level 1.2 for the frame size 320 X 240. The required rate is equal to 690 kbps for a H.264 level 3.1 and 540 kb/s for the H.265 codec. The rate indicated by the parameter b = AS is the maximum rate. m=video 49154 RTP/AVP 98 97 100 99 b=AS: 690 a=rtpmap : 100 H264/90000 a=fmtp: 100 profile-level-id=42e01f a=imageattr: 100 send x=848,y=480] recv [x=848,y=480] a=rtpmap 99 H264/90000 a=fmtp 99 profile-level-id=42e01 a=imageattr:99 send x=320,y=240] recv [x=320,y=240] a=rtpmap: 98 H265/90000 a=fmtp