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Merge pull request #832 from wader/mp4-ctts-signed

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mp4: ctts v0 sample_offset seems to be signed in practice
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Mattias Wadman 2023-12-08 18:18:47 +01:00 committed by GitHub
commit ebf809c045
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 25 additions and 3 deletions
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6
format/mp4/boxes.go
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@ -878,10 +878,10 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
var i uint64
d.FieldStructArrayLoop("entries", "entry", func() bool { return i < entryCount }, func(d *decode.D) {
d.FieldS32("sample_count")
// ISO/IEC14496-12 says version 0 is unsigned and version 1 is signed
// in preactice it seems muxers write it as signed for both version
switch version {
case 0:
d.FieldU32("sample_offset")
case 1:
case 0, 1:
d.FieldS32("sample_offset")
}
i++

BIN
format/mp4/testdata/ctts_v0_signed vendored Normal file
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22
format/mp4/testdata/ctts_v0_signed.fqtest vendored Normal file
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@ -0,0 +1,22 @@
$ fq -d mp4 -o force=true dv ctts_v0_signed
|00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: ctts_v0_signed (mp4) 0x0-0x30 (48)
| | | boxes[0:1]: 0x0-0x30 (48)
| | | [0]{}: box 0x0-0x30 (48)
0x00|00 00 00 30 |...0 | size: 48 0x0-0x4 (4)
0x00| 63 74 74 73 | ctts | type: "ctts" (Composition time to sample) 0x4-0x8 (4)
0x00| 00 | . | version: 0 0x8-0x9 (1)
0x00| 00 00 00 | ... | flags: 0 0x9-0xc (3)
0x00| 00 00 00 04| ....| entry_count: 4 0xc-0x10 (4)
| | | entries[0:4]: 0x10-0x30 (32)
| | | [0]{}: entry 0x10-0x18 (8)
0x10|00 00 00 01 |.... | sample_count: 1 0x10-0x14 (4)
0x10| 00 00 00 0a | .... | sample_offset: 10 0x14-0x18 (4)
| | | [1]{}: entry 0x18-0x20 (8)
0x10| 00 00 00 01 | .... | sample_count: 1 0x18-0x1c (4)
0x10| ff ff ff f6| ....| sample_offset: -10 0x1c-0x20 (4)
| | | [2]{}: entry 0x20-0x28 (8)
0x20|00 00 00 01 |.... | sample_count: 1 0x20-0x24 (4)
0x20| 00 00 00 0a | .... | sample_offset: 10 0x24-0x28 (4)
| | | [3]{}: entry 0x28-0x30 (8)
0x20| 00 00 00 01 | .... | sample_count: 1 0x28-0x2c (4)
0x20| ff ff ff f6| ....| sample_offset: -10 0x2c-0x30 (4)