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MP4WriteSample

NAME

MP4WriteSample - Write a track sample

SYNTAX

#include <mp4.h>

bool MP4WriteSample(
       MP4FileHandle hFile,

       MP4TrackId trackId,

       u_int8_t* pBytes,

       u_int32_t numBytes,

       MP4Duration duration = MP4_INVALID_DURATION,

       MP4Duration renderingOffset = 0,

       bool isSyncSample = true

);

ARGUMENTS

hFile

Specifies the mp4 file to which the operation applies.

trackId

Specifies the track to which the operation applies.

pBytes

Pointer to the sample data.

numBytes

The size in bytes of the sample.

duration

The duration for this sample. Caveat: The duration should be in the track timescale units.

renderingOffset

The rendering offset for this sample. Currently the only media type that needs this feature is MPEG video. Caveat: The offset should be in the track timescale units.

isSyncSample

The sync/random access flag for this sample.

RETURN VALUES

Upon success, true (1). Upon an error, false (0).

DESCRIPTION

MP4WriteSample writes the given sample at the end of the specified track. Currently the library does not support random insertion of samples into the track timeline. Note that with mp4 there cannot be any holes or overlapping samples in the track timeline. The last three arguments give optional sample information.

The value of duration can be given as MP4_INVALID_DURATION if all samples in the track have the same duration. This can be specified with MP4AddTrack() and related functions.

Typically for audio none of the optional arguments are needed. MPEG audio such as MP3 or AAC has a fixed sample duration and every sample can be accessed at random.

For video, all of the optional arguments could be needed. MPEG video can be encoded at a variable frame rate, with only occasional random access points, and with "B frames" which cause the rendering (display) order of the video frames to differ from the storage/decoding order.

Other media types fall between these two extremes.

SEE ALSO

MP4(3)