Are "mp2v" and "mpgv" valid MPEG-2 codec tags in an MOV? This question is related to What is the correct MPEG-2 FourCC? and to an open discussion currently on the ffmpeg-user mailing list:


  I am wondering if I should file a bug report about the MOV output. Open 
  questions in that vein, though, are: 
  
  ...
  
  
  Is it a bug that mpg2 and mpgv cause MOV output to fail or is that 
  correct behavior? 
  


There seem to be numerous possible tags in use for MPEG-2 video, in particular m2v1, mp2v, mpg2, and mpgv.

Now, ffmpeg fails with e.g. "Tag mpgv/0x7667706d incompatible with 
output codec id '2' (m2v1)" when the output is MOV and either mpg2 or mpgv is specified:

ffmpeg ... -vcodec mpeg2video -f mov ...             # succeeds (m1v1)
ffmpeg ... -vcodec mpeg2video -vtag mp2v -f mov ...  # succeeds
ffmpeg ... -vcodec mpeg2video -vtag mpg2 -f mov ...  # fails
ffmpeg ... -vcodec mpeg2video -vtag mpgv -f mov ...  # fails


All of those succeed for AVI. Ffmpeg's default tag for MPEG-2 in AVIs is mpg2.

Part of a bug report that I am writing for ffmpeg's MOV output handling may include the mpg2 and mpgv failure behavior (with the desired behavior being success), but before I do that I need to be certain that this behavior is a bug rather than appropriate behavior.

So my question boils down to this: Are mpg2 and mpgv valid, allowable alternative tags for MPEG-2 video in an MOV file, and are there others? I am looking for official Apple sources and MOV specifications rather than anecdotal evidence or lists of generally observed FourCC's / codec IDs.

I know that, at least according to Wikipedia, MPEG-2 video in an MOV is an acceptable combination, I'm just not sure what the acceptable set of codec tags are in MOVs. This question is not about the "correct" MPEG-2 ID in general cases, it is about the allowable variants specifically in MOVs.
MPEG-2 doesn't seem to be an officially sanctioned codec for the Quicktime container. The official specification has a section related to MPEG-1 in MOV but not MPEG-2. The US Library of Congress also does not have an entry for the subtype MPEG-2 in MOV, like it does for MPEG-1 (just called QTV_MPEG).

So, there's no official word on "allowable alternative tags". One can only examine MPEG-2 MOVs and see whether apps, specifically, Apple apps, play them or not and prepare a survey report. Since each app has its own fiat on whether it plays a file with a certain codec ID or not, that report whould be categorized by app i.e. VLC, Quicktime player. FCP..etc.

As an example, VLC recognizes the following tags for generic MPEG-2 i.e. not IMX or XDCAM:

    A("mpeg"),
    A("mp2v"),
    A("MPEG"),
    A("mpg2"),
    A("MPG2"),
    A("H262"),