If the output sample MIME type is inferred from the input
but is not supported by the muxer, we fallback to transcoding
to a supported sample MIME type.
The audio and video renderers need to make sure not to select the PassthroughSamplePipeline for this case. Which sample MIME type
to choose is decided by the EncoderFactory.
PiperOrigin-RevId: 423272812
