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Old 15th November 2013, 12:32   #1  |  Link
xkfz007
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Join Date: Sep 2013
Posts: 38
What is the exactly CBR in x264?

Today I read some material from Internet about rate control of x264 and I learned what is the ABR mode. When only the param --bitrate is set, ABR mode is used. But I am confused about the CBR mode.
At first I think when the params --vbv-maxrate and --vbv-bufsize are set together with --bitrate , the CBR mode is used. Then I see these codes from x264:
Code:
  s += sprintf( s, " rc=%s mbtree=%d", p->rc.i_rc_method == X264_RC_ABR ?
                               ( p->rc.b_stat_read ? "2pass" : p->rc.i_vbv_max_bitrate == p->rc.i_bitrate ? "cbr" : "abr" )
                               : p->rc.i_rc_method == X264_RC_CRF ? "crf" : "cqp", p->rc.b_mb_tree );
Apparently, only the situation that vbv-maxrate equals bitrate, it is CBR. When the vbv-maxrate is greater than bitrate, it is still ABR mode. I want to confirm if it is correct.
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