ISO/IEC 23001-7 lays out the common encryption standard or 'cenc'. Within this standard, there are several different schemes, confusingly, one of these is also known as 'cenc'. When implementing parts of cbcs support in bug 1487416 I set the [init data type](https://searchfox.org/mozilla-central/rev/e7d9a8749303b39dadcc0e18ea0d60a570a68145/dom/media/mp4/Index.cpp#145) we expose to `cbcs`. I believe this is incorrect, and that the type should be `cenc`. In this case the usage of 'cenc' refers to the init data format in the overall spec, and not something specific to the 'cenc' scheme. I.e. the data in the pssh box is in the safe format if the 'cenc' or 'cbcs' schemes are used, and thus should have the same 'cenc' init data type.
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ISO/IEC 23001-7 lays out the common encryption standard or 'cenc'. Within this standard, there are several different schemes, confusingly, one of these is also known as 'cenc'. When implementing parts of cbcs support in bug 1487416 I set the [init data type](https://searchfox.org/mozilla-central/rev/e7d9a8749303b39dadcc0e18ea0d60a570a68145/dom/media/mp4/Index.cpp#145) we expose to `cbcs`. I believe this is incorrect, and that the type should be `cenc`. In this case the usage of 'cenc' refers to the init data format in the overall spec, and not something specific to the 'cenc' scheme. I.e. the data in the pssh box is in the same format if the 'cenc' or 'cbcs' schemes are used and this is the data we surface in the encrypted event, thus should have the same 'cenc' init data type.