Struct re_video::demux::Sample

pub struct Sample {
    pub is_sync: bool,
    pub sample_idx: usize,
    pub frame_nr: usize,
    pub decode_timestamp: Time,
    pub presentation_timestamp: Time,
    pub duration: Time,
    pub byte_offset: u32,
    pub byte_length: u32,
}

A single sample in a video.

This is equivalent to MP4’s definition of a single sample. Note that in MP4, each sample is forms a single access unit, see 3.1.1 ISO_IEC_14496-14:

3.1.1 Elementary Stream Data To maintain the goals of streaming protocol independence, the media data is stored in its most ‘natural’ format, and not fragmented. This enables easy local manipulation of the media data. Therefore media-data is stored as access units, a range of contiguous bytes for each access unit (a single access unit is the definition of a ‘sample’ for an MPEG-4 media stream).

Access units in H.264/H.265 are always yielding a single frame upon decoding, see https://en.wikipedia.org/wiki/Network_Abstraction_Layer#Access_Units/:

A set of NAL units in a specified form is referred to as an access unit. The decoding of each access unit results in one decoded picture.

Fields

is_sync: bool

Is this the start of a new GroupOfPictures?

This probably means this is a keyframe, and that and entire frame can be decoded from only this one sample (though I’m not 100% sure).

sample_idx: usize

Which sample is this in the video?

This is the order of which the samples appear in the container, which is usually ordered by Self::decode_timestamp.

frame_nr: usize

Which frame does this sample belong to?

This is on the assumption that each sample produces a single frame, which is true for MP4.

This is the index of samples ordered by Self::presentation_timestamp.

decode_timestamp: Time

Time at which this sample appears in the decoded bitstream, in time units.

Samples should be decoded in this order.

decode_timestamp <= presentation_timestamp

presentation_timestamp: Time

Time at which this sample appears in the frame stream, in time units. Often synonymous with presentation_timestamp.

The frame should be shown at this time.

decode_timestamp <= presentation_timestamp

duration: Time

Duration of the sample, in time units.

byte_offset: u32

Offset into the video data.

byte_length: u32

Length of sample starting at Sample::byte_offset.

Implementations

impl Sample

pub fn get(&self, data: &[u8]) -> Option<Chunk>

Read the sample from the video data.

Note that data must be a reference to the original MP4 file from which the VideoData was loaded.

Returns None if the sample is out of bounds, which can only happen if data is not the original video data.

Trait Implementations

impl Clone for Sample

fn clone(&self) -> Sample

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Sample

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.