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Merged
blahspam merged 3 commits into from
Mar 16, 2025
Merged

docs: fix README #85

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ba29125
docs: fix examples: use correct paths, use correct (current) code, sh…
julijane Mar 14, 2025
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Merge branch 'main' into fix-docs
blahspam Mar 16, 2025
9bcfffd
Merge branch 'main' into fix-docs
blahspam Mar 16, 2025
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269 changes: 145 additions & 124 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ The results can be output as a:
* XML - compliant with the [SCTE 35 XML Schema](./docs/scte_35_20220816.xsd)
* JSON - for integrating with JSON based tools such as [jq](https://stedolan.github.io/jq/)

[decode.go](../examples/decode.go)
[examples/simple_decode/main.go](examples/simple_decode/main.go)

```go
package main
Expand All @@ -54,7 +54,7 @@ func main() {
sis, _ := scte35.DecodeBase64("/DA8AAAAAAAAAP///wb+06ACpQAmAiRDVUVJAACcHX//AACky4AMEERJU0NZTVdGMDQ1MjAwMEgxAQEMm4c0")

// details
_, _ = fmt.Fprintf(os.Stdout, "\nDetails: \n%s\n", sis)
_, _ = fmt.Fprintf(os.Stdout, "\nTable: \n%s\n", sis.Table("", "\t"))

// xml
b, _ := xml.MarshalIndent(sis, "", "\t")
Expand All @@ -67,96 +67,94 @@ func main() {
```

```shell
$ go run ./examples/decode.go
$ go run examples/simple_decode/main.go

Details:
Table:
splice_info_section() {
table_id: 0xfc
section_syntax_indicator: false
private_indicator: false
sap_type: Not Specified
section_length: 60 bytes
table_id: 0xfc
section_syntax_indicator: false
private_indicator: false
sap_type: 3 (Not Specified)
section_length: 60
}
protocol_version: 0
encrypted_packet: false
encryption_algorithm: No encryption
pts_adjustment: 0 ticks (0s)
encryption_algorithm: 0 (No encryption)
pts_adjustment: 0
cw_index: 0
tier: 4095
splice_command_length: 5 bytes
splice_command_length: 5
splice_command_type: 0x06
time_signal() {
time_specified_flag: true
pts_time: 3550479013 ticks (10h57m29.766811111s)
time_specified_flag: true
pts_time: 3550479013
}
descriptor_loop_length: 38 bytes
avail_descriptor() {
splice_descriptor_tag: 0x02
descriptor_length: 36 bytes
identifier: CUEI
segmentation_event_id: 39965
segmentation_event_cancel_indicator: false
program_segmentation_flag: true
segmentation_duration_flag: true
delivery_not_restricted_flag: true
segmentation_duration: 10800000 ticks (2m0s)
segmentation_upid_length: 16 bytes
segmentation_upid {
segmentation_upid_type: MPU() (0x0c)
format_identifer: DISC
segmentation_upid: 0x44495343594d57463034353230303048
}
segmentation_type_id: Provider Advertisement End (0x31)
segment_num: 1
segments_expected: 1
descriptor_loop_length: 38
segmentation_descriptor() {
splice_descriptor_tag: 0x02
descriptor_length: 36
identifier: 0x43554549 (CUEI)
segmentation_event_id: 39965
segmentation_event_cancel_indicator: false
segmentation_event_id_compliance_indicator: false
program_segmentation_flag: true
segmentation_duration_flag: true
delivery_not_restricted_flag: true
segmentation_duration: 10800000
segmentation_upid_length: 16
segmentation_upid[0] {
segmentation_upid_type: 0x0c (MPU())
format_identifier: DISC
segmentation_upid: WU1XRjA0NTIwMDBI
}
segmentation_type_id: 0x31 (Provider Advertisement End)
segment_num: 1
segments_expected: 1
}

XML:

XML:
<SpliceInfoSection xmlns="http://www.scte.org/schemas/35" sapType="3" tier="4095">
<EncryptedPacket xmlns="http://www.scte.org/schemas/35" encryptionAlgorithm="0" cwIndex="0"></EncryptedPacket>
<TimeSignal xmlns="http://www.scte.org/schemas/35">
<SpliceTime xmlns="http://www.scte.org/schemas/35" ptsTime="3550479013"></SpliceTime>
</TimeSignal>
<SegmentationDescriptor xmlns="http://www.scte.org/schemas/35" segmentationEventId="39965" segmentationDuration="10800000" segmentationTypeId="49" segmentNum="1" segmentsExpected="1">
<SegmentationUpid xmlns="http://www.scte.org/schemas/35" segmentationUpidType="12" segmentationUpidFormat="base-64" formatIdentifier="1145656131">WU1XRjA0NTIwMDBI</SegmentationUpid>
</SegmentationDescriptor>
<EncryptedPacket xmlns="http://www.scte.org/schemas/35" encryptionAlgorithm="0" cwIndex="0"></EncryptedPacket>
<TimeSignal xmlns="http://www.scte.org/schemas/35">
<SpliceTime xmlns="http://www.scte.org/schemas/35" ptsTime="3550479013"></SpliceTime>
</TimeSignal>
<SegmentationDescriptor xmlns="http://www.scte.org/schemas/35" segmentationEventId="39965" segmentationDuration="10800000" segmentationTypeId="49" segmentNum="1" segmentsExpected="1">
<SegmentationUpid xmlns="http://www.scte.org/schemas/35" segmentationUpidType="12" segmentationUpidFormat="base-64" formatIdentifier="1145656131">WU1XRjA0NTIwMDBI</SegmentationUpid>
</SegmentationDescriptor>
</SpliceInfoSection>

JSON:
JSON:
{
"protocolVersion": 0,
"ptsAdjustment": 0,
"sapType": 3,
"spliceCommand": {
"type": 6,
"spliceTime": {
"ptsTime": 3550479013
}
},
"spliceDescriptors": [
{
"type": 2,
"deliveryRestrictions": null,
"segmentationUpids": [
{
"segmentationUpidType": 12,
"formatIdentifier": 1145656131,
"format": "base-64",
"value": "WU1XRjA0NTIwMDBI"
}
],
"components": null,
"segmentationEventId": 39965,
"segmentationEventCancelIndicator": false,
"segmentationDuration": 10800000,
"segmentationTypeId": 49,
"segmentNum": 1,
"segmentsExpected": 1,
"subSegmentNum": null,
"subSegmentsExpected": null
}
],
"tier": 4095
"encryptedPacket": {
"encryptionAlgorithm": 0,
"cwIndex": 0
},
"sapType": 3,
"spliceCommand": {
"type": 6,
"spliceTime": {
"ptsTime": 3550479013
}
},
"spliceDescriptors": [
{
"type": 2,
"segmentationUpids": [
{
"segmentationUpidType": 12,
"segmentationUpidFormat": "base-64",
"formatIdentifier": 1145656131,
"value": "WU1XRjA0NTIwMDBI"
}
],
"segmentationEventId": 39965,
"segmentationDuration": 10800000,
"segmentationTypeId": 49,
"segmentNum": 1,
"segmentsExpected": 1
}
],
"tier": 4095
}
```

Expand All @@ -166,7 +164,7 @@ Encoding signals is equally simple. You can start from scratch and build a
`scte35.SpliceInfoSection` or decode an existing signal and modify it to suit
your needs.

[encode.go](./examples/encode.go)
[examples/simple_encode/main.go](examples/simple_encode/main.go)

```go
package main
Expand Down Expand Up @@ -197,9 +195,12 @@ func main() {
SegmentNum: 2,
},
},
EncryptedPacket: scte35.EncryptedPacket{CWIndex: 255},
Tier: 4095,
SAPType: 3,
EncryptedPacket: scte35.EncryptedPacket{
EncryptionAlgorithm: scte35.EncryptionAlgorithmNone,
CWIndex: 255,
},
Tier: 4095,
SAPType: 3,
}

// encode it
Expand All @@ -216,20 +217,18 @@ func main() {
)

// encode it again
_, _ = fmt.Fprintf(os.Stdout, "\nModified:\n")
_, _ = fmt.Fprintf(os.Stdout, "Original:\n")
_, _ = fmt.Fprintf(os.Stdout, "base-64: %s\n", sis.Base64())
_, _ = fmt.Fprintf(os.Stdout, "hex : %s\n", sis.Hex())
}

```

```shell
$ go run ./examples/encode.go
$ go run examples/simple_encode/main.go
Original:
base-64: /DAvAAAAAAAA///wBQb+cr0AUAAZAhdDVUVJSAAAjn+PCAg3ODUxMTQ1MjQCADhqB9E=
hex : fc302f000000000000fffff00506fe72bd005000190217435545494800008e7f8f08083738353131343532340200386a07d1

Modified:
Original:
base-64: /DA7AAAAAAAA///wBQb+cr0AUAAlAhdDVUVJSAAAjn+PCAg3ODUxMTQ1MjQCAAEKQ1VFSQCfQUJDKqtwQlQ=
hex : fc303b000000000000fffff00506fe72bd005000250217435545494800008e7f8f08083738353131343532340200010a43554549009f4142432aab704254
```
Expand All @@ -240,7 +239,7 @@ The SCTE 35 decoder will always return a non-nil `SpliceInfoSection`, even when
an error occurs. This is done to help better identify the specific cause of the
decoding failure.

[bad-signal](./examples/bad_signal.go)
[examples/bad_signal/main.go](examples/bad_signal/main.go)

```go
package main
Expand All @@ -249,79 +248,101 @@ import (
"fmt"
"os"

"code.comcast.com/jbaile223/scte35/pkg/scte35"
"github.com/Comcast/scte35-go/pkg/scte35"
)

func main() {
sis, err := scte35.DecodeBase64("FkC1lwP3uTQD0VvxHwVBEH89G6B7VjzaZ9eNuyUF9q8pYAIXsRM9ZpDCczBeDbytQhXkssQstGJVGcvjZ3tiIMULiA4BpRHlzLGFa0q6aVMtzk8ZRUeLcxtKibgVOKBBnkCbOQyhSflFiDkrAAIp+Fk+VRsByTSkPN3RvyK+lWcjHElhwa9hNFcAy4dm3DdeRXnrD3I2mISNc7DkgS0ReotPyp94FV77xMHT4D7SYL48XU20UM4bgg==")
if err != nil {
fmt.Fprintf(os.Stdout, "Error: %s\n", err)
_, _ = fmt.Fprintf(os.Stdout, "Error: %s\n", err)
}
// splice info section contains best-effort decoding
fmt.Fprintf(os.Stdout, "Signal: %s", sis)
_, _ = fmt.Fprintf(os.Stdout, "%s\n", sis.Table("", "\t"))
}
```

As we can see from the output below, the signal has a corrupted `component_count`,
causing the decoder to return a `scte.ErrBufferOverflow`:

```shell
$ go run ./examples/bad_signal.go
$ go run examples/bad_signal/main.go
Error: splice_insert: buffer overflow
Signal: splice_info_section() {
table_id: 0xfc
section_syntax_indicator: false
private_indicator: false
sap_type: Type 1
section_length: 343 bytes
splice_info_section() {
table_id: 0xfc
section_syntax_indicator: false
private_indicator: false
sap_type: 0 (Type 1)
section_length: 347
}
protocol_version: 151
encrypted_packet: false
encryption_algorithm: No encryption
pts_adjustment: 8451077123 ticks (26h5m0.856922222s)
encryption_algorithm: 1 (DES – ECB mode)
pts_adjustment: 8451077123
cw_index: 209
tier: 1471
splice_command_length: 326 bytes
splice_command_length: 326
splice_command_type: 0x05
splice_insert() {
splice_event_id: 1091600189
splice_event_cancel_indicator: false
out_of_network_indicator: true
program_splice_flag: false
duration_flag: true
splice_immediate_flag: false
component_count: 123
component[0] {
component_tag: 86
time_specified_flag: false
splice_event_id: 1091600189
splice_event_cancel_indicator: false
out_of_network_indicator: true
program_splice_flag: false
duration_flag: true
splice_immediate_flag: false
component_count: 123
component[0]
component_tag: 86
time_specified_flag: false
}

... additional components removed

component[122] {
component_tag: 0
time_specified_flag: false
}
auto_return: false
duration: 0 ticks (0s)
unique_program_id: 0
avail_num: 0
avails_expected: 0
auto_return: false
duration: 0
unique_program_id: 0
avail_num: 0
avails_expected: 0
}
descriptor_loop_length: 0
```

#### CRC_32 Validation

The SCTE 35 decoder performs automatic `CRC_32` validation. The returned error
can be explicitly ignored if desired.

[examples/ignore_crc32/main.go](examples/ignore_crc32/main.go)

```go
sis, err := scte35.DecodeBase64("/DA4AAAAAAAAAP/wFAUABDEAf+//mWEhzP4Azf5gAQAAAAATAhFDVUVJAAAAAX+/AQIwNAEAAKeYO3Q=")
if err != nil && !errors.Is(err, scte35.ErrCRC32Invalid) {
return err
package main

import (
"errors"
"fmt"
"os"

"github.com/Comcast/scte35-go/pkg/scte35"
)

func main() {
scte35.Logger.SetOutput(os.Stdout)

sis, err := scte35.DecodeBase64("/DA4AAAAAAAAAP/wFAUABDEAf+//mWEhzP4Azf5gAQAAAAATAhFDVUVJAAAAAX+/AQIwNAEAAKeYO3Q=")
if errors.Is(err, scte35.ErrCRC32Invalid) {
_, _ = fmt.Fprintf(os.Stderr, "Warning: CRC32 check failed!\n")
}
_, _ = fmt.Fprintf(os.Stdout, "%s\n", sis.Table("", "\t"))
}
```

```shell
$ go run examples/ignore_crc32/main.go
2025/03/15 00:44:42 CRC_32 calculated (2811771763) != reported (2811771764)
Warning: CRC32 check failed!
splice_info_section() {
table_id: 0xfc

... more output removed ...
```

#### Logging

Additional diagnostics can be enabled by redirecting the output of
Expand Down
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