Multimedia file stream block structures

This topic describes the structures in the stream block of a multimedia file. A subset of these structures is returned by mmGetFileInfo.

This topic contains the following information:

General structure of a stream block
Level 1: Block header structure
Level 2: Stream header structure
Level 3: Media format structures
Level 4: Codec-specific structures

General structure of a stream block

The following table shows the general structure of a stream block:

Block	Structure	Quantity	Description
blkHeader	FILE_INFO_BLOCK_HEADER	1	Block header, with type and size of the block.
header	FILE_INFO_STREAM_HEADER	1	Stream or track global information.
format	FILE_INFO_FORMAT_AUDIO or FILE_INFO_FORMAT_VIDEO	1	Audio or video stream format information.
codec	FILE_INFO_CODEC_AMR or union of FILE_INFO_CODEC_H263 or FILE_INFO_CODEC_MPEG4	0 or 1	Codec-specific information.

Level 1: Block header structure

Level 1 contains block header information that identifies the block as a stream block and contains the total size of the block. This information is contained in the FILE_INFO_BLOCK_HEADER structure.

Definition

typedef struct
{
WORD blkSize;
WORD blkType;
#define BLK_TYPE_PRESENTATION 1
#define BLK_TYPE_STREAM 2
} FILE_INFO_BLOCK_HEADER;

Fields

Field	Description
blkSize	Total size of the block in which this header is included, in bytes.
blkType	Identifies the block of information. BLK_STREAM identifies the block as a stream block.

Level 2: Stream header structure

Level 2 contains header information specific to a stream, including the type of codec used by the stream. The information is contained in the FILE_INFO_STREAM_HEADER structure.

Definition

typedef struct
{
    WORD blkSize;
    WORD streamType;
#define STREAM_TYPE_UNKNWN 0
#define STREAM_TYPE_AUDIO 1
#define STREAM_TYPE_VIDEO 2
    WORD codec;
#define S_CODEC_UNKNWN 0
#define S_CODEC_AMR 1
#define S_CODEC_AAC 2
#define S_CODEC_H263 3
#define S_CODEC_MPEG4 4
#define S_CODEC_AMR_WB 5
#define S_CODEC_AMR_WB_EXT 6
#define S_CODEC_H264 7
    DWORD streamID;
    DWORD creationTime;
    DWORD duration;
    DWORD rate;
    WORD altGroupID;
    WORD swiGroupID;
    WORD selectAttributes;
#define SELECT_ATTR_LANGUAGE 0x0001
#define SELECT_ATTR_BANDWIDTH 0x0002
#define SELECT_ATTR_CODEC 0x0004
#define SELECT_ATTR_SCREENSIZE 0x0008
#define SELECT_ATTR_MAXPKTSIZE 0x0010
#define SELECT_ATTR_STREAMTYPE 0x0020
    DWORD duration;
    DWORD rate;
    char handlerName [8];
    DWORD sampleSize;
#define SAMPLE_SIZE_VARIABLE 0
    DWORD sampleCount;
    DWORD maxSampleSize;
    DWORD byteCount;
    DWORD flags;
    DWORD startDelay;
} FILE_INFO_STREAM_HEADER;

Fields

Field	Description
blkSize	Total size of the FILE_INFO_STREAM_HEADER block, in bytes. The default value is 44.
streamType	Type of stream. Determines whether the stream block is an audio or video stream block. Valid values: STREAM_TYPE_UNKNWN - Ignore the rest of the stream block. STREAM_TYPE_AUDIO - Stream block is a video block. STREAM_TYPE_VIDEO - Stream block is an audio stream block.
codec	Type of codec. Determines whether the codec structure is an audio or video structure. Valid values: CODEC_UNKNWN - Ignore the rest of the stream block. CODEC_AMR - Codec is AMR. CODEC_H263 - Codec is H.263. CODEC_MPEG4 - Codec is MPEG-4.
streamID	Identifier of the stream or track.
creationTime	Creation date of the stream or track.
altGroupID	Reserved for future use.
swiGroupID	Reserved for future use.
selectAttributes	Reserved for future use.
duration	Play duration of the stream or track.
rate	Sampling rate for audio stream (in Hz) or frame rate for video stream (in frames per second).
handlerName	Media handler name.
sampleSize	Size of the sample. The value is 0 (zero) if the size is variable.
sampleCount	Number of samples in the stream.
maxSampleSize	Size of the largest sample in the stream. The value is 0 (zero) if the information is not available.
byteCount	Total number of bytes in the stream or track.
flags	Reserved for future use.
startdelay	Reserved for future use.

Level 3: Media format structures

Level 3 contains the following media format structures:

FILE_INFO_FORMAT_AUDIO
FILE_INFO_FORMAT_VIDEO

The structure used depends on the codec specified in the stream header.

Note: When new fields are added, the blkSize field of blkHeader must reflect the new size of the block.

FILE_INFO_FORMAT_AUDIO

Contains audio-specific stream format information. It is always present in an audio stream block, and is common to all audio codecs.

Definition

typedef struct

    WORD blkSize;
    WORD channelCount;
    #define CHANNEL_COUNT_MONO 1
    #define CHANNEL_COUNT_STEREO 2
    #define CHANNEL_COUNT_51 6
    WORD sampleSize;
    WORD flags;
FILE_INFO_FORMAT_AUDIO;

Fields

Field	Description
blkSize	Total size of the FILE_INFO_FORMAT_AUDIO block, in bytes. The default value is 10.
channelCount	Number of audio channels: 1 = CHANNEL_COUNT_MONO 2 = CHANNEL_COUNT_STEREO 6 = CHANNEL_COUNT_51
sampleSize	Number of bits per audio sample.
flags	Reserved for future use.

FILE_INFO_FORMAT_VIDEO

Contains video-specific stream format information. It is always present in a video stream block, and is common to all video codecs.

Definition

typedef struct
{
    WORD blkSize;
    WORD width;
    WORD height;
    INT16 layer;
    WORD hResolution;
    WORD vResolution;
    DWORD flags;
} FILE_INFO_FORMAT_VIDEO;

Fields

Field	Description
blkSize	Total size of the FILE_INFO_FORMAT_VIDEO block, in bytes. The default value is 20.
width	Picture width, in pixels. For example, 176 for QCIF.
height	Picture height, in pixels. For example, 144 for QCIF.
layer	Front-to-back ordering. 0 is the normal view. Negative values are in front.
hResolution	Picture horizontal resolution, in pixels per inch. For example, 72.
vResolution	Picture vertical resolution in pixels per inch. For example, 72.
flags	Reserved for future use.

Level 4: Codec-specific structures

Level 4 contains the following codec information structures:

FILE_INFO_CODEC_AMR
FILE_INFO_CODEC_H263
FILE_INFO_CODEC_MPEG4

The structure used depends on the codec specified in the stream header.

FILE_INFO_CODEC_AMR

Contains AMR codec information.

Definition

typedef struct
{
    WORD modeSet; /* bitmap of AMR modes possibly present in stream. b0=mode 0 etc. */
    #define S_AMR_MODE_475 0x0001
    #define S_AMR_MODE_515 0x0002
    #define S_AMR_MODE_590 0x0004
    #define S_AMR_MODE_670 0x0008
    #define S_AMR_MODE_740 0x0010
    #define S_AMR_MODE_795 0x0020
    #define S_AMR_MODE_102 0x0040
    #define S_AMR_MODE_122 0x0080
    #define S_AMR_MODE_SID 0x0100
    #define S_AMR_MODE_NODATA 0x8000
    #define S_AMR_MODE_ALL 0x81FF
    BYTE modeChangePeriod;
    BYTE framesPerSample;
    char vendor [8];
    // new fields may be added here in future release
} FILE_INFO_CODEC_AMR;

Fields

Field	Description
modeSet	Bitmap of AMR modes that can be present in the stream. Valid values: AMR_MODE_475 - Mode 0, 4.75 kbit/s. AMR_MODE_515 - Mode 1, 5.15 kbit/s. AMR_MODE_590 - Mode 2 - 5.90 kbit/s. AMR_MODE_670 - Mode 3, 6.70 kbit/s. AMR_MODE_740 - Mode 4, 7.40 kbit/s. AMR_MODE_795 - Mode 5, 7.95 kbit/s. AMR_MODE_102 - Mode 6, 10.2 kbit/s. AMR_MODE_122 - Mode 7, 12.2 kbit/s. AMR_MODE_SID- Mode 8, AMR SID. AMR_MODE_NODATA - No data. AMR_MODE_ALL - All modes may be present.
modeChangePeriod	A value of 0 (zero) specifies no restriction.
framesPerSample	Number of frames per sample.
vendor	Four-character string representing the codec's manufacturer.

FILE_INFO_CODEC_H263

Contains H.263 codec information.

Definition

typedef struct
{
    BYTE level;
    BYTE profile;
    DWORD avgBitrate;
    DWORD maxBitrate;
    char vendor [8];
    // new fields may be added here in future release
} FILE_INFO_CODEC_H263;

Fields

Field	Description
level	H.263 standard level. Valid values are 10, 20, and 30.
profile	H.263 profile. The only valid value is 0.
avgBitrate	Reserved for future use.
maxBitrate	Reserved for future use.
vendor	Reserved for future use.

FILE_INFO_CODEC_H264

Contains H.264 codec information.

Definition

typedef struct
{
WORD dcStreamType;
WORD dcSpecInfoSize;
#define MMFI_MAX_H264_DCI_SZ 1024
BYTE pDcSpecInfo[MMFI_MAX_H264_DCI_SZ];
WORD dcSpecInfoSize3gppFormat;
BYTE pDcSpecInfo3gppFormat[MMFI_MAX_H264_DCI_SZ];
BYTE level;
} FILE_INFO_CODEC_H264;

Fields

Field	Description
dcStreamType	streamType field of the MPEG-4 DecoderConfig descriptor.
dcSpecInfoSize	Size of decoder specific information, in bytes.
pDcSpecInfo	Points to specific information found in the MPEG-4 DecoderConfig descriptor.
dcSpecInfoSize3gppFormat	Size of decoder specific information, 3gpp format, in bytes. The 3gpp format version contains H.264 start codes.
pDcSpecInfo3gppFormat	Points to specific information found in the MPEG-4 DecoderConfig descriptor, 3gpp format.
level	H.264 level.

FILE_INFO_CODEC_MPEG4

Contains MPEG-4 codec information.

Definition

typedef struct
{
    WORD dcStreamType;
    WORD dcBufferSize;
    DWORD dcAvgBitrate;
    DWORD dcMaxBitrate;
    WORD dcSpecInfoSize;
#define MMFI_MAX_MPEG4_DCI_SZ 128
    BYTE pDcSpecInfo[MMFI_MAX_MPEG4_DCI_SZ];

BYTE level;
} FILE_INFO_CODEC_MPEG4;

Fields

Field	Description
dcStreamType	streamType field of the MPEG-4 DecoderConfig descriptor.
dcBufferSize	Maximum size of sample, in bytes, as indicated in the MPEG-4 DecoderConfig descriptor. For example, minimum size of the decoder buffer.
dcAvgBitrate	Average bitrate, as indicated in the MPEG-4 DecoderConfig descriptor.
dcMaxBitrate	Maximum bitrate, as indicated in the MPEG-4 DecoderConfig descriptor.
dcSpecInfoSize	Size of decoder specific information, in bytes.
pDcSpecInfo	Points to specific information found in the MPEG-4 DecoderConfig descriptor. If present, this data is stored at the end of the current stream block.
level	MPEG-4 level.