Image Chunks
The actual image frames are stored after the "movi" string in the AMF header. If the image compression type is LZC, LZG, LZIV, or LZ8, then timing information is inserted between image data. Timing chunks are stored as JUNK chunks, consisting of the following:
- The string "JUNK".
- A four-byte value indicating the length of this chunk, stored least significant byte (LSB) first. AMF version 1.0 files have length values of 4, versions 2.0 and 3.0 files have length values of 8.
- A four-byte value. In a version 1.0 file, this is a floating point number indicating the time at this frame. On UNIX platforms using version 1.0, this value must be byte swapped after reading. In version 2.0 and 3.0 files, this is an integer, stored LSB first, indicating the number identifier of this frame.
- A four-byte floating point number indicating the time at this frame (version 2.0 and higher only).
- LZC: Lempel-Ziv compression on a 24 bit color image.
- LZIV or LZG: Lempel-Ziv compression on a grayscale image.
- JPEG: JPEG compression.
- LZ8: Lempel-Ziv compression on an 8 bit (256 color) image.
Legend
- Light Green
- Size of the JUNK chunk used for timing info. This is a 4-byte long integer value stored least significant byte (LSB) first.
- Royal Blue
- The time value for this frame. This value is only read in version 1.0 files. It is present but ignored in version 2.0 or higher, as the timing value for those versions comes from the AMF footer structure elsewhere in the file.
- Purple
- Frame number. A 4-byte integer stored LSB first.
- Cyan
- The string value "00db".
- Red
- The size of the image chunk, in bytes, as stored in this file. A four-byte value stored LSB first.
- Yellow
- The compressed size of the image data. A four-byte value stored LSB first.
- Dark Blue
- The uncompressed size of the image data. A four-byte value stored LSB first.
- Dark Green
- Denotes the beginning of the image data.
Legend
- Cyan
- The string value "00db".
- Red
- The size of the image chunk, in bytes, as stored in this file. A four-byte value stored LSB first.
- Yellow
- Denotes the beginning of the image data.