=== Bitstream Data Block (`BITS`)

The `BITS` block contains a list of all known bitstream captures.

A *bitstream* is derived by interpreting flux transitions using an encoding scheme timing table.
While bitstreams sit below sector-level data in the hierarchy, they are still a higher abstraction than raw flux transitions.

Storing bitstream data is valuable because multiple dumps from the same media often produce inconsistent and incomparable flux transitions.
However, once decoded into bitstreams—regardless of whether sector-level user data can be extracted—the results remain consistent and comparable.

Bitstream-level representations are also preferred in low-level emulation scenarios.
Emulators, such as floppy drive emulators, can reconstruct original media more effectively using bitstream data than flux data.

Bitstream data is stored in `DataBlocks` with the `bitstream` data type.
Each image must contain exactly one deduplication table of this data type, and that table must have a single level.

NOTE: Bitstream deduplication tables provide a reference for associating bitstream captures and their corresponding data blocks.

==== Structure Definition

[source,c]
/* Undefined */

==== Field Descriptions

[cols="2,2,2,6",options="header"]
|===
|Type
|Size
|Name
|Description

|uint32_t
|4 bytes
|identifier
|The bitstream data block identifier, always `BITS`

|uint16_t
|2 bytes
|entries
|The number of entries following this header

|uint64_t
|8 bytes
|crc64
|The CRC64-ECMA checksum of the data following this header
|===

==== Bitstream entries

[source,c]
/* Undefined */

==== Field Descriptions

[cols="2,2,2,6",options="header"]
|===
|Type
|Size
|Name
|Description

|uint32_t
|4 bytes
|head
|Head the data corresponds to.

|uint16_t
|2 bytes
|track
|Track the data corresponds to.

|uint8_t
|1 byte
|subtrack
|Substep of a track that the data corresponds to.

|uint64_t
|8 bytes
|tableEntry
|Entry number in the deduplication table where the data corresponding to this bitstream entry is stored
|===

To better understand the relationship between user data, bitstream data and flux data please refer to _Annex F_.