63 lines
2.4 KiB
Go
63 lines
2.4 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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// MediaDataBox Media Data Box
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//
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// 8.1.1 Media Data Box
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// Box Type: ‘mdat’
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// Container: File
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// Mandatory: No
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// Quantity: Zero or more
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//
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// This box contains the media data. In video tracks, this box would contain video frames. A presentation
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// may contain zero or more Media Data Boxes. The actual media data follows the type field; its structure
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// is described by the metadata (see particularly the sample table, subclause 8.5, and the item location box,
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// subclause 8.11.3).
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//
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// In large presentations, it may be desirable to have more data in this box than a 32‐bit size would permit.
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// In this case, the large variant of the size field, above in subclause 4.2, is used.
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//
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// There may be any number of these boxes in the file (including zero, if all the media data is in other files).
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// The metadata refers to media data by its absolute offset within the file (see subclause 8.7.5, the Chunk
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// Offset Box); so Media Data Box headers and free space may easily be skipped, and files without any box
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// structure may also be referenced and used.
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type MediaDataBox struct {
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*Box
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ContentStartPosition uint64
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ContentEndPosition uint64
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}
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// BoxTypeMediaData Media Data Box
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const BoxTypeMediaData = "mdat"
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func init() {
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BoxDefinitions = append(BoxDefinitions, BoxDefinition{
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Type: BoxTypeMediaData,
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ParentTypes: []string{boxTypeParentFile},
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Parser: ParseMediaDataBox,
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})
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}
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// ParseMediaDataBox creates a new media data box struct
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func ParseMediaDataBox(parser *Parser, filePosition uint64, headerSize uint32, content []byte) (any, error) {
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box := &MediaDataBox{Box: &Box{filePosition, headerSize}}
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// parse positions of content
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box.ContentStartPosition = filePosition + uint64(headerSize)
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box.ContentEndPosition = box.ContentStartPosition + uint64(len(content))
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return box, nil
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}
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