| 1 | # Media Source Extensions Notes
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| 2 | A collection of findings experimenting with Media Source Extensions on
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| 3 | Chrome 36.
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| 4 |
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| 5 | * Specifying an audio and video codec when creating a source buffer
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| 6 | but passing in an initialization segment with only a video track
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| 7 | results in a decode error
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| 8 |
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| 9 | ## ISO Base Media File Format (BMFF)
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| 10 |
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| 11 | ### Init Segment
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| 12 | A working initialization segment is outlined below. It may be possible
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| 13 | to trim this structure down further.
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| 14 |
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| 15 | - `ftyp`
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| 16 | - `moov`
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| 17 | - `mvhd`
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| 18 | - `trak`
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| 19 | - `tkhd`
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| 20 | - `mdia`
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| 21 | - `mdhd`
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| 22 | - `hdlr`
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| 23 | - `minf`
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| 24 | - `mvex`
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| 25 |
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| 26 | ### Media Segment
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| 27 | The structure of a minimal media segment that actually encapsulates
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| 28 | movie data is outlined below:
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| 29 |
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| 30 | - `moof`
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| 31 | - `mfhd`
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| 32 | - `traf`
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| 33 | - `tfhd`
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| 34 | - `tfdt`
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| 35 | - `trun` containing samples
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| 36 | - `mdat`
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| 37 |
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| 38 | ### Structure
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| 39 |
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| 40 | sample: time {number}, data {array}
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| 41 | chunk: samples {array}
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| 42 | track: samples {array}
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| 43 | segment: moov {box}, mdats {array} | moof {box}, mdats {array}, data {array}
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| 44 |
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| 45 | track
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| 46 | chunk
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| 47 | sample
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| 48 |
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| 49 | movie fragment -> track fragment -> [samples]
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| 50 |
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| 51 | ### Sample Data Offsets
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| 52 | Movie-fragment Relative Addressing: all trun data offsets are relative
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| 53 | to the containing moof (?).
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| 54 |
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| 55 | Without default-base-is-moof, the base data offset for each trun in
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| 56 | trafs after the first is the *end* of the previous traf.
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| 57 |
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| 58 | #### iso5/DASH Style
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| 59 | moof
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| 60 | |- traf (default-base-is-moof)
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| 61 | | |- trun_0 <size of moof> + 0
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| 62 | | `- trun_1 <size of moof> + 100
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| 63 | `- traf (default-base-is-moof)
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| 64 | `- trun_2 <size of moof> + 300
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| 65 | mdat
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| 66 | |- samples_for_trun_0 (100 bytes)
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| 67 | |- samples_for_trun_1 (200 bytes)
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| 68 | `- samples_for_trun_2
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| 69 |
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| 70 | #### Single Track Style
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| 71 | moof
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| 72 | `- traf
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| 73 | `- trun_0 <size of moof> + 0
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| 74 | mdat
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| 75 | `- samples_for_trun_0 |
| \ | No newline at end of file |