add T_QUICKTIME codec mapping #112

dericed · 2017-03-14T19:10:07Z

intended as alternative to #102

dericed · 2017-03-14T19:15:52Z

Related message at https://mailarchive.ietf.org/arch/msg/cellar/flGPjiu-YBdpAgDQ-IUZNBY1wfk

dericed · 2017-09-16T23:09:12Z

This PR was rewritten to split T_QUICKTIME into T_QUICKTIME/SINGLE and T_QUICKTIME/MULTIPLE. The SINGLE version only uses a single Cluster and timecode value to associate a virtual continuous QuickTime timecode with the Matroska timecode. This is the way most QuickTime timecode tracks work, a single value stored, and every other value calculated based off private data. The MULTIPLE version infers that more than one value may be stored. I may add some example math here but wanted some review of the concepts here. Ping to @JeromeMartinez.

retokromer · 2017-09-17T05:57:16Z

codec_specs.md

+
+Codec Name: QuickTime timecode track (continuous)
+
+Description: `T_QUICKTIME/SINGLE` is used to identify Timecode tracks as stored in QuickTime. The `QuickTime Timecode Sample Data` is stored within the Block's data section. For an explanation of `QuickTime Timecode Sample Data` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-57421). In the context of Matroska, `T_QUICKTIME/SINGLE` tracks MUST only relate to exactly one `Cluster` which MUST have a `Cluster Timecode` of zero and exactly one `SimpleBlock` or `BlockGroup Element`. The storage of the `QuickTime Timecode Sample Data` with the `SimpleBlock` or `BlockGroup Element` allows the `QuickTime Timecode` to be mapped to the `Matroska Timecode` at a single point. The `QuickTime Timecode` value MAY then be evaluated at any point in the `Matroska Timecode` by using the initialised `Timecode Sample Description`, the single `QuickTime Timecode Sample Data` value, and the `Matroska Timecode`.


British initialised or American initialized? The rest seems to me American.

Two things I'd like to discuss:

In the context of Matroska, T_QUICKTIME/SINGLE tracks MUST only relate to exactly one Cluster which MUST have a Cluster Timecode of zero and exactly one SimpleBlock or BlockGroup Element.

I honestly don't understand what this is supposed to mean, especially the verb "relate". Do you mean to say that for a track with the CodecID T_QUICKTIME/SINGLE there MUST be exactly one BlockGroup or SimpleBlock, that this singular block is stored in a cluster with ClusterTimecode set to 0, and that there MUST NOT be any other cluster in the file with ClusterTimecode set to 0?

If yes, why such severe restrictions? Why not allow multiple Clusters that start at 0 (by simply omitting the restriction)? What about files whose first cluster doesn't start at 0 — how would that be interpreted? And why are you saying something about the Cluster Timecode but not about the timecode parts of the blocks?

In other words: can you please describe all of your thoughts in much more detail? We can then see how to turn that into unambiguous verbiage.

The second issue I have is with linking to other web pages as part of the format specification. I'd rather we refer to existing PDF documentation or publications. In the case of linking to the QuickTime specification this is both possible and a bit difficult: possible because there is a PDF version of the QuickTime specs, and harder because it doesn't contain numbered chapters and sections. I still prefer to say something like this:

For an explanation of the format read the section "Timecode Media", sub-section "Timecode Sample Description", of Apple's QuickTime File Format Specification (2001).

In this case, I suggest that T_QUICKTIME/SINGLE implies that only a single Cluster is associated with that track. I didn't mean that imply that other tracks could not share the same timecode value. Upon reflection I think the requirement to use a Cluster Timecode is unnecessary. What is needed in T_QUICKTIME/SINGLE is for a single QuickTime Timecode Sample Data value to be stored in a single BlockGroup or SimpleBlock of a single Cluster, then the QuickTime Timecode Sample Data (within the Block) and the Timecode Sample Description (in Private Data) and the Cluster Timecode and the Block Timecode can be used to calculate what the QuickTime Timecode value should be relative to any Matroska Timecode value. Still for a Matroska Reader that needs to quickly associate any Matroska Timecode value with a QuickTime Timecode value it would be good to know where that Cluster is quickly. I had intended to have Cluster as 0 timecode to mean that it should be one of the first Clusters, but of course that is not a good expectation.

If finding the (single) BlockGroup/SimpleBlock is the goal, then just say that the BlockGroup/SimpleBlock SHOULD be referenced via Cues.

I don't like requiring that the first or one of the first cluster contains that data as that seems problematic wrt streaming Matroska files.

Are there any other Codec Mappings that require Cues?

None that I know of.

retokromer · 2017-09-17T05:58:08Z

codec_specs.md

+
+Description: `T_QUICKTIME/SINGLE` is used to identify Timecode tracks as stored in QuickTime. The `QuickTime Timecode Sample Data` is stored within the Block's data section. For an explanation of `QuickTime Timecode Sample Data` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-57421). In the context of Matroska, `T_QUICKTIME/SINGLE` tracks MUST only relate to exactly one `Cluster` which MUST have a `Cluster Timecode` of zero and exactly one `SimpleBlock` or `BlockGroup Element`. The storage of the `QuickTime Timecode Sample Data` with the `SimpleBlock` or `BlockGroup Element` allows the `QuickTime Timecode` to be mapped to the `Matroska Timecode` at a single point. The `QuickTime Timecode` value MAY then be evaluated at any point in the `Matroska Timecode` by using the initialised `Timecode Sample Description`, the single `QuickTime Timecode Sample Data` value, and the `Matroska Timecode`.
+
+Initialisation: The `Private Data` contains the `Timecode Sample Description` which in QuickTime is stored within the 'tmcd' atom after the mandatory `data reference index` value. For an explanation of the `Timecode Sample Description` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-69831).


same here (and below)

Same issue with referencing web pages vs. a published standard (as a PDF).

mbunkus · 2017-09-18T18:53:43Z

codec_specs.md

+
+Codec Name: QuickTime timecode track (continuous)
+
+Description: `T_QUICKTIME/SINGLE` is used to identify Timecode tracks as stored in QuickTime. The `QuickTime Timecode Sample Data` is stored within the Block's data section. For an explanation of `QuickTime Timecode Sample Data` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-57421). In the context of Matroska, `T_QUICKTIME/SINGLE` tracks MUST only relate to exactly one `Cluster` which MUST have a `Cluster Timecode` of zero and exactly one `SimpleBlock` or `BlockGroup Element`. The storage of the `QuickTime Timecode Sample Data` with the `SimpleBlock` or `BlockGroup Element` allows the `QuickTime Timecode` to be mapped to the `Matroska Timecode` at a single point. The `QuickTime Timecode` value MAY then be evaluated at any point in the `Matroska Timecode` by using the initialised `Timecode Sample Description`, the single `QuickTime Timecode Sample Data` value, and the `Matroska Timecode`.


Two things I'd like to discuss:

In the context of Matroska, T_QUICKTIME/SINGLE tracks MUST only relate to exactly one Cluster which MUST have a Cluster Timecode of zero and exactly one SimpleBlock or BlockGroup Element.

I honestly don't understand what this is supposed to mean, especially the verb "relate". Do you mean to say that for a track with the CodecID T_QUICKTIME/SINGLE there MUST be exactly one BlockGroup or SimpleBlock, that this singular block is stored in a cluster with ClusterTimecode set to 0, and that there MUST NOT be any other cluster in the file with ClusterTimecode set to 0?

If yes, why such severe restrictions? Why not allow multiple Clusters that start at 0 (by simply omitting the restriction)? What about files whose first cluster doesn't start at 0 — how would that be interpreted? And why are you saying something about the Cluster Timecode but not about the timecode parts of the blocks?

In other words: can you please describe all of your thoughts in much more detail? We can then see how to turn that into unambiguous verbiage.

mbunkus · 2017-09-18T18:58:58Z

codec_specs.md

+
+Codec Name: QuickTime timecode track (continuous)
+
+Description: `T_QUICKTIME/SINGLE` is used to identify Timecode tracks as stored in QuickTime. The `QuickTime Timecode Sample Data` is stored within the Block's data section. For an explanation of `QuickTime Timecode Sample Data` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-57421). In the context of Matroska, `T_QUICKTIME/SINGLE` tracks MUST only relate to exactly one `Cluster` which MUST have a `Cluster Timecode` of zero and exactly one `SimpleBlock` or `BlockGroup Element`. The storage of the `QuickTime Timecode Sample Data` with the `SimpleBlock` or `BlockGroup Element` allows the `QuickTime Timecode` to be mapped to the `Matroska Timecode` at a single point. The `QuickTime Timecode` value MAY then be evaluated at any point in the `Matroska Timecode` by using the initialised `Timecode Sample Description`, the single `QuickTime Timecode Sample Data` value, and the `Matroska Timecode`.


The second issue I have is with linking to other web pages as part of the format specification. I'd rather we refer to existing PDF documentation or publications. In the case of linking to the QuickTime specification this is both possible and a bit difficult: possible because there is a PDF version of the QuickTime specs, and harder because it doesn't contain numbered chapters and sections. I still prefer to say something like this:

For an explanation of the format read the section "Timecode Media", sub-section "Timecode Sample Description", of Apple's QuickTime File Format Specification (2001).

mbunkus · 2017-09-18T18:59:35Z

codec_specs.md

+
+Description: `T_QUICKTIME/SINGLE` is used to identify Timecode tracks as stored in QuickTime. The `QuickTime Timecode Sample Data` is stored within the Block's data section. For an explanation of `QuickTime Timecode Sample Data` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-57421). In the context of Matroska, `T_QUICKTIME/SINGLE` tracks MUST only relate to exactly one `Cluster` which MUST have a `Cluster Timecode` of zero and exactly one `SimpleBlock` or `BlockGroup Element`. The storage of the `QuickTime Timecode Sample Data` with the `SimpleBlock` or `BlockGroup Element` allows the `QuickTime Timecode` to be mapped to the `Matroska Timecode` at a single point. The `QuickTime Timecode` value MAY then be evaluated at any point in the `Matroska Timecode` by using the initialised `Timecode Sample Description`, the single `QuickTime Timecode Sample Data` value, and the `Matroska Timecode`.
+
+Initialisation: The `Private Data` contains the `Timecode Sample Description` which in QuickTime is stored within the 'tmcd' atom after the mandatory `data reference index` value. For an explanation of the `Timecode Sample Description` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-69831).


Same issue with referencing web pages vs. a published standard (as a PDF).

mcr · 2020-03-31T19:51:54Z

This may require changes in Matroksa, and it may not be possible to do this in the same document.

dericed · 2020-04-30T15:07:27Z

I think this idea is much lower priority (and perhaps unneeded) since there #348. Close?

JeromeMartinez · 2020-04-30T15:14:09Z

I think this idea is much lower priority (and perhaps unneeded) since there #348. Close?

The "format" is different between QuickTime time code (there is a CodecPrivate part with "24Hours" etc flags, then an offset from 00:00:00) and SMPTE ST 12 (hours, minutes, seconds, frames), and conversion can be lossy e.g. if hours count is 30 (possible in QuickTime, not possible in SMPTE ST 12).

Low priority: right.
Unneeded: I disagree, not the same target of users (one is lossless transwrapping from QuickTime, the other is lossless transwrapping from MXF).

They are just 2 different formats with no bijection between them.

robUx4

we need to tell the track type to use

robUx4 · 2021-03-14T08:55:00Z

codec_specs.md

@@ -23,6 +23,7 @@ Video      | "V_"
 Audio      | "A_"
 Subtitle   | "S_"
 Button     | "B_"
+Timecode   | "T_"


There is currently no "timecode" track type. There is a "metadata" track type which seems to be fitting. So maybe the prefix should be "M_" and the type called Metadata ?

We can also add a "timecode" track type. In the end it's more informational for the player what this is about, although it should be able to tell what kind of metadata we're talking about just by looking at the codec. But at the container level (don't know what's in codecs) it might be usefull to tell if we have timecodes or not.

robUx4 · 2021-03-14T08:56:09Z

codec_specs.md

+
+### T_QUICKTIME/SINGLE
+
+Codec ID: T_QUICKTIME/SINGLE


We need to tell what track type to use "metadata", "subtitle", "timecode" ? Maybe this should be explained in the chapter above.

robUx4 · 2024-12-22T13:28:27Z

Moving this to Matroska v5 because:

timecode is not an existing track type
the codec doesn't exist yet
this may be a new block addition

robUx4 added the codec mapping label Jul 14, 2017

dericed force-pushed the T_QUICKTIME branch from f3e95cc to 951a5e2 Compare September 16, 2017 23:07

retokromer reviewed Sep 17, 2017

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mbunkus requested changes Sep 18, 2017

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robUx4 added the spec_codecs Codec Matroska spec document target label Dec 18, 2018

mcr added the new_document Might go in a new document of its own label Mar 31, 2020

robUx4 requested changes Mar 14, 2021

View reviewed changes

add T_QUICKTIME codec mappings

a607eaf

robUx4 force-pushed the T_QUICKTIME branch from 951a5e2 to a607eaf Compare March 14, 2021 08:58

robUx4 force-pushed the master branch from 5b4360d to 7c1fdea Compare December 29, 2022 16:11

robUx4 added the matroska-v5 label Dec 22, 2024

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add T_QUICKTIME codec mapping #112

add T_QUICKTIME codec mapping #112

dericed commented Mar 14, 2017

dericed commented Mar 14, 2017

dericed commented Sep 16, 2017

retokromer Sep 17, 2017

mbunkus Sep 18, 2017

mbunkus Sep 18, 2017

dericed Sep 24, 2017

mbunkus Sep 25, 2017

dericed Sep 25, 2017

mbunkus Sep 25, 2017

retokromer Sep 17, 2017 •

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mbunkus Sep 18, 2017

mbunkus Sep 18, 2017

mbunkus Sep 18, 2017

mbunkus Sep 18, 2017

mcr commented Mar 31, 2020

dericed commented Apr 30, 2020

JeromeMartinez commented Apr 30, 2020

robUx4 left a comment

robUx4 Mar 14, 2021

robUx4 Mar 14, 2021

robUx4 commented Dec 22, 2024


		Codec Name: QuickTime timecode track (continuous)

		Description: `T_QUICKTIME/SINGLE` is used to identify Timecode tracks as stored in QuickTime. The `QuickTime Timecode Sample Data` is stored within the Block's data section. For an explanation of `QuickTime Timecode Sample Data` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-57421). In the context of Matroska, `T_QUICKTIME/SINGLE` tracks MUST only relate to exactly one `Cluster` which MUST have a `Cluster Timecode` of zero and exactly one `SimpleBlock` or `BlockGroup Element`. The storage of the `QuickTime Timecode Sample Data` with the `SimpleBlock` or `BlockGroup Element` allows the `QuickTime Timecode` to be mapped to the `Matroska Timecode` at a single point. The `QuickTime Timecode` value MAY then be evaluated at any point in the `Matroska Timecode` by using the initialised `Timecode Sample Description`, the single `QuickTime Timecode Sample Data` value, and the `Matroska Timecode`.


		Description: `T_QUICKTIME/SINGLE` is used to identify Timecode tracks as stored in QuickTime. The `QuickTime Timecode Sample Data` is stored within the Block's data section. For an explanation of `QuickTime Timecode Sample Data` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-57421). In the context of Matroska, `T_QUICKTIME/SINGLE` tracks MUST only relate to exactly one `Cluster` which MUST have a `Cluster Timecode` of zero and exactly one `SimpleBlock` or `BlockGroup Element`. The storage of the `QuickTime Timecode Sample Data` with the `SimpleBlock` or `BlockGroup Element` allows the `QuickTime Timecode` to be mapped to the `Matroska Timecode` at a single point. The `QuickTime Timecode` value MAY then be evaluated at any point in the `Matroska Timecode` by using the initialised `Timecode Sample Description`, the single `QuickTime Timecode Sample Data` value, and the `Matroska Timecode`.

		Initialisation: The `Private Data` contains the `Timecode Sample Description` which in QuickTime is stored within the 'tmcd' atom after the mandatory `data reference index` value. For an explanation of the `Timecode Sample Description` read [QuickTime File Format Specification](https://developer.apple.com/library/content/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-69831).

add T_QUICKTIME codec mapping #112

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add T_QUICKTIME codec mapping #112

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dericed commented Mar 14, 2017

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robUx4 commented Dec 22, 2024

retokromer Sep 17, 2017 •

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