AVISTREAMHEADER Structure

The AVISTREAMHEADER structure contains information about one stream in an AVI file.

Syntax

typedef struct _avistreamheader {
     FOURCC fcc;
     DWORD  cb;
     FOURCC fccType;
     FOURCC fccHandler;
     DWORD  dwFlags;
     WORD   wPriority;
     WORD   wLanguage;
     DWORD  dwInitialFrames;
     DWORD  dwScale;
     DWORD  dwRate;
     DWORD  dwStart;
     DWORD  dwLength;
     DWORD  dwSuggestedBufferSize;
     DWORD  dwQuality;
     DWORD  dwSampleSize;
     struct {
         short int left;
         short int top;
         short int right;
         short int bottom;
     }  rcFrame;
} AVISTREAMHEADER;

Members

fcc

Specifies a FOURCC code. The value must be 'strh'.

cb

Specifies the size of the structure, not including the initial 8 bytes.

fccType

Contains a FOURCC that specifies the type of the data contained in the stream. The following standard AVI values for video and audio are defined.

fccHandler

Optionally, contains a FOURCC that identifies a specific data handler. The data handler is the preferred handler for the stream. For audio and video streams, this specifies the codec for decoding the stream.

dwFlags

Contains any flags for the data stream. The bits in the high-order word of these flags are specific to the type of data contained in the stream. The following standard flags are defined.

dwPriority

Specifies priority of a stream type. For example, in a file with multiple audio streams, the one with the highest priority might be the default stream.

dwInitialFrames

Specifies how far audio data is skewed ahead of the video frames in interleaved files. Typically, this is about 0.75 seconds. If you are creating interleaved files, specify the number of frames in the file prior to the initial frame of the AVI sequence in this member. For more information about the contents of this member, see "Special Information for Interleaved Files" in the Video for Windows Programmer's Guide.

dwScale

Used with dwRate to specify the time scale that this stream will use. Dividing dwRate by dwScale gives the number of samples per second. For video streams, this is the frame rate. For audio streams, this rate corresponds to the time needed to play nBlockAlign bytes of audio, which for PCM audio is the just the sample rate.

dwRate

See dwScale.

dwStart

Specifies the starting time for this stream. The units are defined by the dwRate and dwScale members in the main file header. Usually, this is zero, but it can specify a delay time for a stream that does not start concurrently with the file.

dwLength

Specifies the length of this stream. The units are defined by the dwRate and dwScale members of the stream's header.

dwSuggestedBufferSize

Specifies how large a buffer should be used to read this stream. Typically, this contains a value corresponding to the largest chunk present in the stream. Using the correct buffer size makes playback more efficient. Use zero if you do not know the correct buffer size.

dwQuality

Specifies an indicator of the quality of the data in the stream. Quality is represented as a number between 0 and 10,000. For compressed data, this typically represents the value of the quality parameter passed to the compression software. If set to –1, drivers use the default quality value.

dwSampleSize

Specifies the size of a single sample of data. This is set to zero if the samples can vary in size. If this number is nonzero, then multiple samples of data can be grouped into a single chunk within the file. If it is zero, each sample of data (such as a video frame) must be in a separate chunk. For video streams, this number is typically zero, although it can be nonzero if all video frames are the same size. For audio streams, this number should be the same as the nBlockAlign member of the WAVEFORMATEX structure describing the audio.

rcFrame

Specifies the destination rectangle for a text or video stream within the movie rectangle specified by the dwWidth and dwHeight members of the AVI main header structure. The rcFrame member is typically used in support of multiple video streams. Set this rectangle to the coordinates corresponding to the movie rectangle to update the whole movie rectangle. Units for this member are pixels. The upper-left corner of the destination rectangle is relative to the upper-left corner of the movie rectangle.

Remarks

Some of the members of this structure are also present in the AVIMAINHEADER structure. The data in the AVIMAINHEADER structure applies to the whole file, while the data in the AVISTREAMHEADER structure applies to one stream.

Requirements

Include Aviriff.h

See Also

• AVI RIFF File Reference
• DirectShow Structures