111 lines
4.8 KiB
Go
111 lines
4.8 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 (
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"encoding/binary"
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"time"
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)
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// MovieHeaderBox Movie Header Box struct
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//
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// 8.2.2 Movie Header Box
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// Box Type: ‘mvhd’
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// Container: Movie Box (‘moov’)
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// Mandatory: Yes
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// Quantity: Exactly one
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//
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// This box defines overall information which is media‐independent, and relevant to the entire
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// presentation considered as a whole.
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type MovieHeaderBox struct {
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*FullBox
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// is an integer that declares the creation time of the presentation (in seconds
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// since midnight, Jan. 1, 1904, in UTC time)
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CreationTimeV0 time.Time
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// is an integer that declares the creation time of the presentation (in seconds
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// since midnight, Jan. 1, 1904, in UTC time)
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CreationTimeV1 time.Time
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// is an integer that declares the most recent time the presentation was
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// modified (in seconds since midnight, Jan. 1, 1904, in UTC time)
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ModificationTimeV0 time.Time
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// is an integer that declares the most recent time the presentation was
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// modified (in seconds since midnight, Jan. 1, 1904, in UTC time)
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ModificationTimeV1 time.Time
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// is an integer that specifies the time‐scale for the entire presentation; this is the
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// number of time units that pass in one second. For example, a time coordinate system that
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// measures time in sixtieths of a second has a time scale of 60.
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Timescale uint32
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// is an integer that declares length of the presentation (in the indicated timescale). This
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// property is derived from the presentation’s tracks: the value of this field corresponds to the
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// duration of the longest track in the presentation. If the duration cannot be determined then
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// duration is set to all 1s.
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DurationV0 uint32
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// is an integer that declares length of the presentation (in the indicated timescale). This
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// property is derived from the presentation’s tracks: the value of this field corresponds to the
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// duration of the longest track in the presentation. If the duration cannot be determined then
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// duration is set to all 1s.
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DurationV1 uint64
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// is a fixed point 16.16 number that indicates the preferred rate to play the presentation; 1.0
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// (0x00010000) is normal forward playback
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Rate Fixed1616
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// is a fixed point 8.8 number that indicates the preferred playback volume. 1.0 (0x0100) is
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// full volume.
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Volume Fixed88
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// provides a transformation matrix for the video; (u,v,w) are restricted here to (0,0,1), hex
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// values (0,0,0x40000000).
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Matrix []int32
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// is a non‐zero integer that indicates a value to use for the track ID of the next track
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// to be added to this presentation. Zero is not a valid track ID value. The value of
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// next_track_ID shall be larger than the largest track‐ID in use. If this value is equal to all 1s
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// (32‐bit maxint), and a new media track is to be added, then a search must be made in the file for
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// an unused track identifier.
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NextTrackID uint32
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}
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// ParseMovieHeaderBox creates a new Movie Header Box struct
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func ParseMovieHeaderBox(filePosition uint64, headerSize uint32, content []byte) *MovieHeaderBox {
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box := &MovieHeaderBox{
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FullBox: newFullBox(&Box{filePosition, headerSize}, content[0:4]),
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}
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position := 4
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if box.Version == 1 {
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box.CreationTimeV1 = since1904ToTime(int64(binary.BigEndian.Uint64(content[4:12])))
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box.ModificationTimeV1 = since1904ToTime(int64(binary.BigEndian.Uint64(content[12:20])))
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box.Timescale = binary.BigEndian.Uint32(content[20:24])
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box.DurationV1 = binary.BigEndian.Uint64(content[24:32])
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position += 28
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} else { // version == 0
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box.CreationTimeV0 = since1904ToTime(int64(binary.BigEndian.Uint32(content[4:8])))
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box.ModificationTimeV0 = since1904ToTime(int64(binary.BigEndian.Uint32(content[8:12])))
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box.Timescale = binary.BigEndian.Uint32(content[12:16])
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box.DurationV0 = binary.BigEndian.Uint32(content[16:20])
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position += 16
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}
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box.Rate = NewFixed1616ByBytes(content[position : position+4])
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box.Volume = NewFixed88ByBytes(content[position+4 : position+6])
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position += 4 + 2 + 2 + 8 // 4 bytes for rate, 2 bytes for volume, 2 bytes reserved and 8 bytes reserved
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for i := 0; i < 9; i++ {
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box.Matrix = append(box.Matrix, int32(binary.BigEndian.Uint32(content[position:position+4])))
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position += 4
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}
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// skip 6*32 bit "pre-defined"
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position += 6 * 4
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box.NextTrackID = binary.BigEndian.Uint32(content[position : position+4])
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return box
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}
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