88 lines
3.8 KiB
Go
88 lines
3.8 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 "encoding/binary"
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// TrackFragmentHeaderBox Track Fragment Header
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//
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// 8.8.7 Track Fragment Header Box
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// Box Type: ‘tfhd’
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// Container: Track Fragment Box ('traf')
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// Mandatory: Yes
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// Quantity: Exactly one
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//
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// Each movie fragment can add zero or more fragments to each track; and a track fragment can add zero
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// or more contiguous runs of samples. The track fragment header sets up information and defaults used
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// for those runs of samples.
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//
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// The base‐data‐offset, if explicitly provided, is a data offset that is identical to a chunk offset in the Chunk
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// Offset Box, i.e. applying to the complete file (e.g. starting with a file‐type box and movie box). In
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// circumstances when the complete file does not exist or its size is unknown, it may be impossible to use
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// an explicit base‐data‐offset; then, offsets need to be established relative to the movie fragment.
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type TrackFragmentHeaderBox struct {
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*FullBox
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TrackID uint32
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// the base offset to use when calculating data offsets
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BaseDataOffset uint64
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SampleDescriptionIndex uint32
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DefaultSampleDuration uint32
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DefaultSampleSize uint32
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DefaultSampleFlags uint32
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}
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const (
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// TrackFragmentHeaderBoxFlagBaseDataOffsetPresent Base Offset Present Flag
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//
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// indicates the presence of the base‐data‐offset field. This
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// provides an explicit anchor for the data offsets in each track run (see below). If not provided and
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// if the default‐base‐is‐moof flag is not set, the base‐data‐offset for the first track in the movie
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// fragment is the position of the first byte of the enclosing Movie Fragment Box, and for second
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// and subsequent track fragments, the default is the end of the data defined by the preceding
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// track fragment. Fragments 'inheriting' their offset in this way must all use the same data‐
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// reference (i.e., the data for these tracks must be in the same file)
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TrackFragmentHeaderBoxFlagBaseDataOffsetPresent uint32 = 0x00000001
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// TrackFragmentHeaderBoxFlagSampleDescriptionIndexPresent Sample Description Index Present Flag
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//
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// indicates the presence of this field, which over‐rides,
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// in this fragment, the default set up in the Track Extends Box.
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TrackFragmentHeaderBoxFlagSampleDescriptionIndexPresent uint32 = 0x00000002
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// TrackFragmentHeaderBoxFlagDefaultSampleDurationPresent Default Sample Duration Present Flag
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TrackFragmentHeaderBoxFlagDefaultSampleDurationPresent uint32 = 0x00000008
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// TrackFragmentHeaderBoxFlagDefaultSampleSize Default Sample Size Present Flag
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TrackFragmentHeaderBoxFlagDefaultSampleSize uint32 = 0x00000010
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// TrackFragmentHeaderBoxFlagDefaultSampleFlags Default Sample Flags Present Flag
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TrackFragmentHeaderBoxFlagDefaultSampleFlags uint32 = 0x00000020
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// TODO: define other flags
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)
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// ParseTrackFragmentHeaderBox creates a new track fragment header box struct
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func ParseTrackFragmentHeaderBox(filePosition uint64, headerSize uint32, content []byte) *TrackFragmentHeaderBox {
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box := &TrackFragmentHeaderBox{FullBox: newFullBox(&Box{filePosition, headerSize}, content[0:4])}
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position := 4
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// parse track ID
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box.TrackID = binary.BigEndian.Uint32(content[position : position+4])
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position += 4
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// TODO: check other flags
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return box
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}
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