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mp4: Decode pcmC and chnl box #1082

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merged 1 commit into from
Feb 17, 2025
Merged

mp4: Decode pcmC and chnl box #1082

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101 changes: 93 additions & 8 deletions format/mp4/boxes.go
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Original file line number Diff line number Diff line change
Expand Up @@ -591,13 +591,14 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
size := d.FieldU32("size")
dataFormat := d.FieldUTF8("type", 4, dataFormatNames, scalar.ActualTrimSpace)
subType := ""
if t := ctx.currentTrack(); t != nil {
t.sampleDescriptions = append(t.sampleDescriptions, sampleDescription{
track := ctx.currentTrack()
if track != nil {
track.sampleDescriptions = append(track.sampleDescriptions, sampleDescription{
dataFormat: dataFormat,
})

if t.seenHdlr {
subType = t.subType
if track.seenHdlr {
subType = track.subType
} else {
// TODO: seems to be ffmpeg mov.c, where is this documented in specs?
// no hdlr box found, guess using dataFormat
Expand All @@ -617,7 +618,6 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {

switch subType {
case "soun", "vide":

version := d.FieldU16("version")
d.FieldU16("revision_level")
d.FieldU32("max_packet_size") // TODO: vendor for some subtype?
Expand All @@ -626,9 +626,10 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
case "soun":
// AudioSampleEntry
// https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-SW1
var numAudioChannels uint64
switch version {
case 0:
d.FieldU16("num_audio_channels")
numAudioChannels = d.FieldU16("num_audio_channels")
d.FieldU16("sample_size")
d.FieldU16("compression_id")
d.FieldU16("packet_size")
Expand All @@ -637,7 +638,7 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
decodeBoxes(ctx, d)
}
case 1:
d.FieldU16("num_audio_channels")
numAudioChannels = d.FieldU16("num_audio_channels")
d.FieldU16("sample_size")
d.FieldU16("compression_id")
d.FieldU16("packet_size")
Expand All @@ -657,7 +658,7 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
d.FieldU32("always_65536")
d.FieldU32("size_of_struct_only")
d.FieldF64("audio_sample_rate")
d.FieldU32("num_audio_channels")
numAudioChannels = d.FieldU32("num_audio_channels")
d.FieldU32("always_7f000000")
d.FieldU32("const_bits_per_channel")
d.FieldU32("format_specific_flags")
Expand All @@ -669,6 +670,9 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
default:
d.FieldRawLen("data", d.BitsLeft())
}
if track != nil {
track.stsdNumAudioChannels = numAudioChannels
}
case "vide":
// VideoSampleEntry
// TODO: version 0 and 1 same?
Expand Down Expand Up @@ -1832,6 +1836,87 @@ func decodeBox(ctx *decodeContext, d *decode.D, typ string) {
d.FieldRawLen("uid", 128)
}
})
case "pcmC":
d.FieldU8("version")
d.FieldU24("flags")
d.FieldU8("format_flags")
d.FieldU8("sample_size")
case "chnl":
version := d.FieldU8("version")
d.FieldU24("flags")

if version == 0 {
hasObjects := false
hasChannels := false
d.FieldStruct("stream_structure", func(d *decode.D) {
d.FieldRawLen("unused", 6)
hasObjects = d.FieldBool("objects")
hasChannels = d.FieldBool("channels")
})
if hasChannels {
definedLayout := d.FieldU8("defined_layout")
if definedLayout == 0 {
track := ctx.currentTrack()
if track == nil {
d.FieldRawLen("rest", d.BitsLeft())
break
}
d.FieldArray("channels", func(d *decode.D) {
for i := 0; i < int(track.stsdNumAudioChannels); i++ {
d.FieldStruct("channel", func(d *decode.D) {
speakerPosition := d.FieldU8("speaker_position")
if speakerPosition == 126 {
d.FieldS16("azimuth")
d.FieldS8("elevation")
}
})
}
})
} else {
d.FieldU64("omitted_channels_map")
}
}
if hasObjects {
d.FieldU8("object_count")
}
} else {
hasChannels := false
d.FieldStruct("stream_structure", func(d *decode.D) {
d.FieldRawLen("unused", 2)
d.FieldBool("objects")
hasChannels = d.FieldBool("channels")
})
d.FieldU4("format_ordering")
d.FieldU8("base_channel_count")
if hasChannels {
definedLayout := d.FieldU8("defined_layout")
if definedLayout == 0 {
layoutChannelCount := d.FieldU8("layout_channel_count")
d.FieldArray("channels", func(d *decode.D) {
for i := 0; i < int(layoutChannelCount); i++ {
d.FieldStruct("channel", func(d *decode.D) {
speakerPosition := d.FieldU8("speaker_position")
if speakerPosition == 126 {
d.FieldS16("azimuth")
d.FieldS8("elevation")
}
})
}
})
} else {
d.FieldRawLen("reserved", 4)
d.FieldU3("channel_order_definition")
omittedChannelsPresent := d.FieldBool("omitted_channels_present")
if omittedChannelsPresent {
d.FieldU64("omitted_channels_map")
}
}
}
// if hasObjects {
// // ISO/IEC 14496-12:2022:
// // > object_count is derived from baseChannelCount
// }
}

default:
// there are at least 4 ways to encode udta metadata in mov/mp4 files.
Expand Down
29 changes: 15 additions & 14 deletions format/mp4/mp4.go
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Original file line number Diff line number Diff line change
Expand Up @@ -136,20 +136,21 @@ type stsz struct {
}

type track struct {
seenHdlr bool
fragment bool
id int
sampleDescriptions []sampleDescription
subType string
stco []int64
stsc []stsc
stsz []stsz
formatInArg any
objectType int // if data format is "mp4a"
defaultIVSize int
moofs []*moof // for fmp4
dref bool
drefURL string
seenHdlr bool
fragment bool
id int
sampleDescriptions []sampleDescription
subType string
stco []int64
stsc []stsc
stsz []stsz
formatInArg any
objectType int // if data format is "mp4a"
defaultIVSize int
moofs []*moof // for fmp4
dref bool
drefURL string
stsdNumAudioChannels uint64
}

type pathEntry struct {
Expand Down
Binary file added format/mp4/testdata/chnl-ver1
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18 changes: 18 additions & 0 deletions format/mp4/testdata/chnl-ver1.fqtest
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
$ fq -o force=true -d mp4 dv chnl-ver1
|00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: chnl-ver1 (mp4) 0x0-0x10 (16)
| | | boxes[0:1]: 0x0-0x10 (16)
| | | [0]{}: box 0x0-0x10 (16)
0x00|00 00 00 10 |.... | size: 16 0x0-0x4 (4)
0x00| 63 68 6e 6c | chnl | type: "chnl" 0x4-0x8 (4)
0x00| 01 | . | version: 1 0x8-0x9 (1)
0x00| 00 00 00 | ... | flags: 0 0x9-0xc (3)
| | | stream_structure{}: 0xc-0xc.4 (0.4)
0x00| 11 | . | unused: raw bits 0xc-0xc.2 (0.2)
0x00| 11 | . | objects: false 0xc.2-0xc.3 (0.1)
0x00| 11 | . | channels: true 0xc.3-0xc.4 (0.1)
0x00| 11 | . | format_ordering: 1 0xc.4-0xd (0.4)
0x00| 02 | . | base_channel_count: 2 0xd-0xe (1)
0x00| 02 | . | defined_layout: 2 0xe-0xf (1)
0x00| 00| .| reserved: raw bits 0xf-0xf.4 (0.4)
0x00| 00| .| channel_order_definition: 0 0xf.4-0xf.7 (0.3)
0x00| 00| .| omitted_channels_present: false 0xf.7-0x10 (0.1)
Binary file added format/mp4/testdata/pcmC
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10 changes: 10 additions & 0 deletions format/mp4/testdata/pcmC.fqtest
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
$ fq -o force=true -d mp4 dv pcmC
|00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: pcmC (mp4) 0x0-0xe (14)
| | | boxes[0:1]: 0x0-0xe (14)
| | | [0]{}: box 0x0-0xe (14)
0x0|00 00 00 0e |.... | size: 14 0x0-0x4 (4)
0x0| 70 63 6d 43 | pcmC | type: "pcmC" 0x4-0x8 (4)
0x0| 00 | . | version: 0 0x8-0x9 (1)
0x0| 00 00 00 | ... | flags: 0 0x9-0xc (3)
0x0| 01 | . | format_flags: 1 0xc-0xd (1)
0x0| 18| | .| | sample_size: 24 0xd-0xe (1)