Add Sample demonstrating the use of the new CFR Rate Control mode.

[johndeu]

There are now new Rate control modes on the encoder. It would be great to have a sample showing how to set the CRF mode on the encoder - since that is a common ask. The CBR mode is less commonly asked for, but we have had a few customers that need it to hit a target bitrate.

CRF mode is similar to constrained VBR.

(RateControlMode setting is highlighted and its default value is H264RateControlMode.ABR)

CBR mode: var preset = new StandardEncoderPreset { Codecs = { new AacAudio(), new H264Video() { RateControlMode = H264RateControlMode.CBR, Layers = { new H264Layer { Bitrate = 2000000, Width = "1280", Height = "720" } } } },

     Formats =
     {
       new Mp4Format
      {
         FilenamePattern = "{Basename}_{Bitrate}{Extension}"
       }
     }
   }

CRF mode: var preset = new StandardEncoderPreset { Codecs = { new AacAudio(), new H264Video() { RateControlMode = H264RateControlMode.CRF, Layers = { new H264Layer { Crf = 28, Bitrate = 2000000, Width = "1280", Height = "720" } } } },

Formats = { new Mp4Format { FilenamePattern = "{Basename}_{Bitrate}{Extension}" } } }

[johndeu]

Resolving this one with new sample. Thanks @xpouyat !