This question relates to another one on Super User, where I ask more generally about the relationship between the size of a video file and its other file properties.
For a set of 71 video files, I'm looking at their properties, as reported by the Windows 11 shell. For information on those properties in general, see the StackOverflow Q&A, What are the file properties in the Windows 11 shell?
My question is about the property whose index in Windows 11 is 311 and whose name is "Video compression". For the set of files I'm looking at, I found them to have nine different values:
1. {3147504D-0000-0010-8000-00AA00389B71} Only found for mpg.
2. {31564D57-0000-0010-8000-00AA00389B71} Only found for wmv.
3. {3253344D-0000-0010-8000-00AA00389B71} Found for avi and mp4.
4. {32564D57-0000-0010-8000-00AA00389B71} Only found for wmv.
5. {33564D57-0000-0010-8000-00AA00389B71} Only found for wmv.
6. {34363248-0000-0010-8000-00AA00389B71} Only found for mp4.
7. {53565133-767A-494D-B478-F29D25DC9037} Only found for mov.
8. {5634504D-0000-0010-8000-00AA00389B71} Only found for avi.
9. {E06D8026-DB46-11CF-B4D1-00805F6CBBEA} Only found for mpg.
So while, within this set of files, each value mostly appears for one type of file, that's not completely true because value 3 appears for two types.
Looking at the file type/property value relationship from the other direction, the set of files has the following values of this property:
- Of 4 avi files, three have value 3 and one has value 8.
- Of 2 mov files, they both have value 7.
- Of 45 mp4 files, 44 have value 6 and one has value 3.
- Of 3 mpg files, two have value 9 and one has value 1.
- Of 17 wmv files, ten have value 4, three have 5, and four have 2.
I haven't found any information about this property. It's hard to search for because Googling windows shell "Video compression" brings up a long list of results about video compression that have nothing to do with Windows OS.
So, my question is, what do these property values mean? An ideal answer would link to formal documentation of the property, if that exists.
Edit
Two comments link to pages with lists of GUIDs. I ran a comparison of those GUIDs to the nine values of the property "Video compression" on my files, with the following results:
- The link given by "user23404432" is to an official MS page that associates each GUID with a "global media type identifier". The associations with the "Video compression" values found in my files are as follows:
| # | Video compression | Global media type identifier |
|---|---|---|
| 1 | {3147504D-0000-0010-8000-00AA00389B71} | |
| 2 | {31564D57-0000-0010-8000-00AA00389B71} | WMMEDIASUBTYPE_WMV1 |
| 3 | {3253344D-0000-0010-8000-00AA00389B71} | WMMEDIASUBTYPE_M4S2 |
| 4 | {32564D57-0000-0010-8000-00AA00389B71} | WMMEDIASUBTYPE_WMV2 |
| 5 | {33564D57-0000-0010-8000-00AA00389B71} | WMMEDIASUBTYPE_WMV3 |
| 6 | {34363248-0000-0010-8000-00AA00389B71} | |
| 7 | {53565133-767A-494D-B478-F29D25DC9037} | |
| 8 | {5634504D-0000-0010-8000-00AA00389B71} | |
| 9 | {E06D8026-DB46-11CF-B4D1-00805F6CBBEA} | WMMEDIASUBTYPE_MPEG2_VIDEO |
Thus four of the "Video compression" values found in my files do not correspond to any of the type identifiers given on that page. The page states that it is for a legacy feature that has been superseded, so presumably the list it gives is outdated.
- The link given by Paul is to a page on GitHub with no indication of where its huge amount of data comes from, no date, and nothing else that provides any assurance of being credible and current. The data associate a large number of GUIDs with various formats and with something else called "Caps", which are not defined. The associations of the "Video compression" values on my files with the stated formats are:
| # | Video compression | Video format |
|---|---|---|
| 1 | {3147504D-0000-0010-8000-00AA00389B71} | MPEG-1 Part 2, Video (ISO/IEC 11172-2) |
| 2 | {31564D57-0000-0010-8000-00AA00389B71} | Windows Media Video |
| 3 | {3253344D-0000-0010-8000-00AA00389B71} | MPEG-4 Part 2, MPEG-4 Visual (ISO/IEC 14496-2) |
| 4 | {32564D57-0000-0010-8000-00AA00389B71} | Windows Media Video |
| 5 | {33564D57-0000-0010-8000-00AA00389B71} | Windows Media Video |
| 6 | {34363248-0000-0010-8000-00AA00389B71} | ITU-T H.264/MPEG-4 Part 10, AVC (ISO/IEC 14496-10) |
| 7 | {53565133-767A-494D-B478-F29D25DC9037} | |
| 8 | {5634504D-0000-0010-8000-00AA00389B71} | MPEG-4 Part 2, MPEG-4 Visual (ISO/IEC 14496-2) |
| 9 | {E06D8026-DB46-11CF-B4D1-00805F6CBBEA} | ITU-T H.262/MPEG-2 Part 2, Video (ISO/IEC 13818-2) |
Thus property value 7 does not correspond to any listed GUID, while values 2, 4, and 5 all correspond to one format.
- Neither of the linked pages appear to have anything to do with compression. They appear to indicate that the values of the property "Video compression" are actually GUIDs that indicate a particular media type or format. I suppose that some of the indicated media types or formats might be intrinsically compressed, but if so, these pages don't say so.
I don't think I know any more about the meanings of this property after doing this comparison of its values with the GUIDs listed on those two pages. The closest I come to making any sense of this is that "Video compression" is a misnomer for the property because it does not contain information about compression, but instead contains a GUID that indicates the file's media type or format, and I don't have a list that says which media type or format for all my files.
I want to know if anyone disagrees with this answer, and if better information is available anywhere. This answer was composed based on research on the subject without relevant expertise. For that reason, I have less than full confidence that it is fully correct.
Short answer: The value of the "Video compression" property for a file is a GUID that specifies the video coding format used in the file. The format specifies what compression techniques may be used by a codec implementing that format. In this round-about way, this property specifies what techniques may be used to compress the video data in the file.
Long answer:
The meaning of the Windows shell file property "Video compression" (property index 311 in Windows 11) is cryptic. The values of the property are GUIDs (globally unique identifiers) that represent "media types," which are associated with video coding formats and video codecs. The format or codec used in a video file indicates what compression techniques are used in the file.
There are two references online that indicate the meanings of some GUIDs that appear as values of this property. These references were given in comments on the question.
Media Type Identifiers for the Windows Media Format SDK
Media Foundation and DirectShow Media Types
Among the 71 files discussed in the question, the above references indicate the following associations:
In this table, the links on the names of the ISO specifications are not provided in the reference. The ISO webpages were found by Googling those spec names. The four ISO pages linked to provide brief descriptions of the specs and their histories and allow for the purchase of the spec documents, which have, respectively, 112, 706, 867, and 225 pages, for $245 each. In addition, one of the specs is available for free download, the one for "H.264/MPEG-4 Part 10, AVC" used in most (but not all) mp4 files. The download is an 880-page pdf.
Neither any of the four ISO webpages nor the downloaded document contain the word "codec," but they all talk about coding of moving pictures. Section 0.6.1 of the document says, "The coded representation specified in the syntax [mentioned in Sec. 0.5] is designed to enable a high compression capability for a desired image quality. ... A number of techniques may be used to achieve highly efficient compression. Encoding algorithms (not specified in this document) may ..." (Emphasis added.)
From this I infer that the specs referred to define the syntax to be used by encoding algorithms intended to adhere to those specs, and that those algorithms are what are called "codecs." The defined syntax specifies exactly what compression techniques may be used by the codecs.
If I've understood all of this correctly, this is the round-about way in which those cryptic GUIDs specify what types of compression may be used in the files, which apparently does not necessarily mean that all allowed techniques are actually used in the file.
I hope people who know this stuff better than me will say in comments whether this answer is correct, or will post a better answer or edit this one to fix any errors.
One big problem with this answer is that I haven't found any other reference stating the meanings of those GUIDs other than the two stated above. There has to be a complete and up-to-date list somewhere. I hope someone can provide a link to that.