87 lines
3.1 KiB
Go
87 lines
3.1 KiB
Go
// Copyright 2024 Martin Riedl
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package gomp4
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import (
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"encoding/binary"
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)
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// SampleSizeBox sample size box struct
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//
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// Box Type: ‘stsz’, ‘stz2’
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// Container: Sample Table Box (‘stbl’)
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// Mandatory: Yes
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// Quantity: Exactly one variant must be present
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//
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// This box contains the sample count and a table giving the size in bytes of each sample. This allows the
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// media data itself to be unframed. The total number of samples in the media is always indicated in the
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// sample count.
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//
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// There are two variants of the sample size box. The first variant has a fixed size 32‐bit field for
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// representing the sample sizes; it permits defining a constant size for all samples in a track. The second
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// variant permits smaller size fields, to save space when the sizes are varying but small. One of these
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// boxes must be present; the first version is preferred for maximum compatibility.
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type SampleSizeBox struct {
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*FullBox
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// is integer specifying the default sample size. If all the samples are the same size,
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// this field contains that size value. If this field is set to 0, then the samples have different sizes,
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// and those sizes are stored in the sample size table. If this field is not 0, it specifies the constant
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// sample size, and no array follows.
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SampleSize uint32
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// is an integer that gives the number of samples in the track; if sample‐size is 0, then
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// it is also the number of entries in the following table.
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SampleCount uint32
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// is an integer specifying the size of a sample, indexed by its number.
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SampleSizeList []SampleSizeEntry
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}
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type SampleSizeEntry struct {
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EntrySize uint32
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}
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// BoxTypeSampleSizeBox Sample Size Box
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const BoxTypeSampleSizeBox = "stsz"
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func init() {
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BoxDefinitions = append(BoxDefinitions, BoxDefinition{
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Type: BoxTypeSampleSizeBox,
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ParentTypes: []string{BoxTypeSampleTable},
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Parser: ParseSampleSizeBox,
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})
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}
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// ParseSampleSizeBox creates a new sample size box struct based on bytes
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func ParseSampleSizeBox(parser *Parser, filePosition uint64, headerSize uint32, content []byte) (any, error) {
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box := &SampleSizeBox{
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FullBox: newFullBox(&Box{filePosition, headerSize}, content[0:4]),
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}
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// parse fields
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box.SampleSize = binary.BigEndian.Uint32(content[4:8])
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box.SampleCount = binary.BigEndian.Uint32(content[8:12])
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position := 12
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// parse sample sizes
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if box.SampleSize == 0 {
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for i := 0; i < int(box.SampleCount); i++ {
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sampleEntry := SampleSizeEntry{
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EntrySize: binary.BigEndian.Uint32(content[position+(i*4) : position+4+(i*4)]),
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}
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box.SampleSizeList = append(box.SampleSizeList, sampleEntry)
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}
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}
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return box, nil
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}
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