MMMULTITRACKREAD Operations

The MMMULTITRACKREAD structure contains the following parameters:

• Pointer to the read buffer (pBuffer)
  
• Length of the read buffer (ulLength)
  
• Read flags (ulFlags)
  
• Number of track entries or number of tracks (ulNumTracks)
  
• Pointer to a track map list (pTrackMapList)
  
• Actual buffer length available in MULTITRACKREAD extended mode (ulBufferLength)

The track map list is a list of valid track numbers for the current file and is used to map a track to a record table. Each track map list contains:

• A track ID (ulTrackID) 
  The number of record entries (ulNumEntries)
  
  A pointer to a record table (pRecordTabList)

  Each element of the record table contains a pointer to (pBuffer) and the length (ulLength) of the corresponding data in the buffer.

  For example, if the number of track entries is two, the track map list will contain two track map tables, one for each track. There is a corresponding record table for each track. The number of entries in the track map table for each track is the number of entries in the record table for a particular track. The following figure illustrates the multitrack read data structure.

    MMMULTITRACKREAD
                                                  pBuffer
  ┌───────────────┐ ┌─────────────────────────────────────────┐
  │ ulLength      ├─┘  TRACKMAP         RECORDTAB             │
  │ pBuffer       │    TABLE                  AUDIO           │
  │ ulFlags       │  ┌───────────────┐  ┌────────────┐    ┌───────┐ ┐
  │ ulNumTracks   │  │ ulTrackID     │  │ pRecord  1 ├──── Audio  │ │
  │ pTrackMapList ├── ulNumEntries  ├── ulLength   │    │ Data 1 │ │
  │               │  │ pRecordTabList│  │ ulParm1    │    ├────────┤ │
  │               │  ├───────────────┤  │ ulParm2    │ ┌── Video  │ │
  │ ulBufferLength│  │ ulTrackID     │  ├────────────┤ │  │ Data 1 │ │
  │(extended mode)│  │ ulNumEntries  ├┐ │ .        2 │ │  ├────────┤ │
  └───────────────┘  │ pRecordTabList││ │ .          ├─┼── Audio  │ │
                     ├───────────────┤│ │ .          │ │  │ Data 2 │ │
                     │ .             ││ └────────────┘ │  ├────────┤ │
                     │ .             ││ RECORDTAB      │  │ Video  │ │
                     │ .             ││       VIDEO    │┌─ Data 2 │ │ ulLength
                     └───────────────┘│ ┌────────────┐ ││ ├────────┤ │
                                      │ │ pRecord  1 │ ││ │ .      │ │
                                      └─ ulLength   ├─┘│ │ .      │ │
                                        │ ulParm1    │  │ │ .      │ │
                                        │ ulParm2    │  │ ├────────┤ │
                                        ├────────────┤  │ │        │ │
                                        │ .        2 ├──┘ │        │ │
                                        │ .          │    │        │ │
                                        │ .          │    ├────────┤ │
                                        └────────────┘    │        │ │
                                                          │        │ │
                                                          │        │ │
  MMMULTITRACKREAD                       pBuffer          ├────────┤ │
  ┌───────────────┐ ┌──────────────────────────────────┐  │        │ │
  │ ulLength      ├─┘  TRACKMAP         RECORDTAB      │  │        │ │
  │ pBuffer       │    TABLE                  AUDIO    │  │        │ ┘
  │ ulFlags       │  ┌───────────────┐  ┌────────────┐ └─├────────┤ ┐
  │ ulNumTracks   │  │ ulTrackID     │  │ pRecord  1 ├──── Audio  │ │
  │ pTrackMapList ├── ulNumEntries  ├── ulLength   │    │ Data 1 │ │
  │               │  │ pRecordTabList│  │ ulParm1    │    ├────────┤ │
  │               │  ├───────────────┤  │ ulParm2    │ ┌── Video  │ │
  │ ulBufferLength│  │ ulTrackID     │  ├────────────┤ │  │ Data 1 │ │
  │(extended mode)│  │ ulNumEntries  ├┐ │ .        2 │ │  ├────────┤ │ ulLength
  └───────────────┘  │ pRecordTabList││ │ .          ├─┼── Audio  │ │
                     ├───────────────┤│ │ .          │ │  │ Data 2 │ │
                     │ .             ││ └────────────┘ │  ├────────┤ │
                     │ .             ││ RECORDTAB      │  │ Video  │ │
                     │ .             ││       VIDEO    │┌─ Data 2 │ │
                     └───────────────┘│ ┌────────────┐ ││ ├────────┤ │
                                      │ │ pRecord  1 │ ││ │ .      │ │
                                      └─ ulLength   ├─┘│ │ .      │ │
                                        │ ulParm1    │  │ │ .      │ │
                                        │ ulParm2    │  │ └────────┘ ┘
                                        ├────────────┤  │
                                        │ .        2 ├──┘
                                        │ .          │
                                        │ .          │
                                        └────────────┘
  

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