Phenix Technical Bulletins

Brief updates about using Phenix.

Previously, the default for multi-bitrate transcoding would generate video in both VP8 and H.264 codecs. The default is now to generate only H.264. However, if you would like to continue to generate both H.264 and VP8, use both multi-bitrate-codec=h264 and multi-bitrate-codec=vp8 capabilities.

• The main reason for the new default is better perceived viewing quality of the H.264 codec vs. VP8.

• The use of one codec instead of two reduces CPU load for MBR ladder creation saves cost in cloud transcoding and increases the channel capacity of the Phenix encoding software for the same hardware.

• New Firefox installations that have never previously needed the H.264 codec will asynchronously download H.264 support, causing a one-time failure to play, subsequent playback attempts succeed after the codec is installed.

• Some older Android devices have poor H.264 implementations that may not support NACK and/or FEC for H.264 on par with VP8, which can cause these devices to see more micro freezing using H.264 vs. VP8.

• H.264 can produce a more variable bitrate in constant bitrate mode than VP8. This can cause clients with limited bandwidth to switch down the MBR ladder and receive a reduced resolution stream.