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Merge pull request #558 from wader/mp4-udta-with-no-length

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mp4: udta: Handle box with value rest of box
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Mattias Wadman 2023-01-25 16:34:58 +01:00 committed by GitHub
commit a2cdb3d6c9
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2 changed files with 34 additions and 8 deletions
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30
format/mp4/boxes.go
View File

@ -1647,7 +1647,7 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
}
})
default:
// there are at least 3 ways to encode udta metadata in mov/mp4 files.
// there are at least 4 ways to encode udta metadata in mov/mp4 files.
//
// mdta subtype:
//
@ -1656,7 +1656,7 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
// hdlr with subtype "mdta"
// keys with 1-based <index> to key namespace.name table
// ilst
// <index>-box
// <index>-box (box type is 32bit BE 1-based number into table above)
// data box with value
//
// mdir subtype:
@ -1668,20 +1668,34 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
// ©<abc> or similar
// data with value
//
// no-meta-box:
// no-meta-box with length and language:
//
// udta
// ©<abc> or similar
// data with length, language and value
// value length and language
//
// no-meta-box value rest of box:
//
// udta
// <name>
// value rest of box
if mb := ctx.currentMetaBox(); mb != nil && ctx.parent().typ == "ilst" {
// unknown type under a meta box with ilst as parent, decode as boxes
// is probably one or more data boxes
decodeBoxes(ctx, d)
} else if ctx.parent().typ == "udta" {
length := d.FieldU16("length")
d.FieldStrFn("language", decodeLang)
d.FieldUTF8("value", int(length))
// TODO: better probe? ffmpeg uses box name heuristics?
// if 16 length field seems to match assume box with length, language and value
// otherwise decode as box with value rest of box
probeLength := d.PeekBits(16)
// +2 for length field, +2 for language field
if (probeLength+2+2)*8 == uint64(d.BitsLeft()) {
length := d.FieldU16("length")
d.FieldStrFn("language", decodeLang)
d.FieldUTF8("value", int(length))
} else {
d.FieldUTF8("value", int(d.BitsLeft()/8))
}
} else {
d.FieldRawLen("data", d.BitsLeft())
}

12
format/mp4/testdata/udta_no_length.fqtest vendored Normal file
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@ -0,0 +1,12 @@
# construct udta box with one name box that has no length field
$ fq -n '[0,0,0,53-32,117,100,116,97,0,0,0,45-32,110,97,109,101,"hello"] | tobytes | mp4({force: true}) | d'
|00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: (mp4)
| | | boxes[0:1]:
| | | [0]{}: box
0x00|00 00 00 15 |.... | size: 21
0x00| 75 64 74 61 | udta | type: "udta" (User-data)
| | | boxes[0:1]:
| | | [0]{}: box
0x00| 00 00 00 0d | .... | size: 13
0x00| 6e 61 6d 65| name| type: "name"
0x10|68 65 6c 6c 6f| |hello| | value: "hello"