How to transcode MP4 video with SRT subtitle on AWS Elemental MediaConvert - json

Question

I have a MP4 video with SRT captions and I need to transcode them with media convert. In media convert I set automatic ABR and I specified the SRT origin path.
At the moment, I have tested the following:
I set SRT file in one output and video/audio in another
I set SRT, video and audio in the same output
For the first test, the job finish successfully, but on the S3 bucket there isnt any .SRT file. For the second test, the job fails with "aption destination type [SRT] requires a raw muxer." message
This is my JSON for the first test
{
"Queue": "arn:aws:mediaconvert:us-east-1:{{ACCOUNT-NUMBER}}:queues/Default",
"UserMetadata": {},
"Role": "arn:aws:iam::{{ACCOUNT-NUMBER}}:role/{{MY-ROLE-NAME}}",
"Settings": {
"TimecodeConfig": {
"Source": "ZEROBASED"
},
"OutputGroups": [
{
"Name": "DASH ISO",
"Outputs": [
{
"ContainerSettings": {
"Container": "MPD"
},
"VideoDescription": {
"ScalingBehavior": "DEFAULT",
"TimecodeInsertion": "DISABLED",
"AntiAlias": "ENABLED",
"Sharpness": 50,
"CodecSettings": {
"Codec": "H_264",
"H264Settings": {
"InterlaceMode": "PROGRESSIVE",
"ScanTypeConversionMode": "INTERLACED",
"NumberReferenceFrames": 3,
"Syntax": "DEFAULT",
"Softness": 0,
"GopClosedCadence": 1,
"GopSize": 90,
"Slices": 1,
"GopBReference": "DISABLED",
"SlowPal": "DISABLED",
"EntropyEncoding": "CABAC",
"FramerateControl": "INITIALIZE_FROM_SOURCE",
"RateControlMode": "QVBR",
"CodecProfile": "MAIN",
"Telecine": "NONE",
"MinIInterval": 0,
"AdaptiveQuantization": "AUTO",
"CodecLevel": "AUTO",
"FieldEncoding": "PAFF",
"SceneChangeDetect": "ENABLED",
"QualityTuningLevel": "MULTI_PASS_HQ",
"FramerateConversionAlgorithm": "DUPLICATE_DROP",
"UnregisteredSeiTimecode": "DISABLED",
"GopSizeUnits": "FRAMES",
"ParControl": "INITIALIZE_FROM_SOURCE",
"NumberBFramesBetweenReferenceFrames": 2,
"RepeatPps": "DISABLED",
"DynamicSubGop": "STATIC"
}
},
"AfdSignaling": "NONE",
"DropFrameTimecode": "ENABLED",
"RespondToAfd": "NONE",
"ColorMetadata": "INSERT"
},
"AudioDescriptions": [
{
"AudioTypeControl": "FOLLOW_INPUT",
"AudioSourceName": "Audio Selector 1",
"CodecSettings": {
"Codec": "AAC",
"AacSettings": {
"AudioDescriptionBroadcasterMix": "NORMAL",
"Bitrate": 96000,
"RateControlMode": "CBR",
"CodecProfile": "LC",
"CodingMode": "CODING_MODE_2_0",
"RawFormat": "NONE",
"SampleRate": 48000,
"Specification": "MPEG4"
}
},
"StreamName": "latino",
"LanguageCodeControl": "FOLLOW_INPUT",
"LanguageCode": "SPA"
}
]
},
{
"ContainerSettings": {
"Container": "MPD"
},
"CaptionDescriptions": [
{
"CaptionSelectorName": "Captions Selector 1",
"DestinationSettings": {
"DestinationType": "SRT"
},
"LanguageCode": "SPA",
"LanguageDescription": "latino"
}
]
}
],
"OutputGroupSettings": {
"Type": "DASH_ISO_GROUP_SETTINGS",
"DashIsoGroupSettings": {
"SegmentLength": 30,
"MinFinalSegmentLength": 0,
"Destination": "s3://{{BUCKET-NAME}}/streaming15/dash-iso/",
"FragmentLength": 2,
"SegmentControl": "SINGLE_FILE",
"MpdProfile": "ON_DEMAND_PROFILE",
"HbbtvCompliance": "NONE"
}
},
"AutomatedEncodingSettings": {
"AbrSettings": {
"MaxAbrBitrate": 8000000,
"MinAbrBitrate": 600000
}
}
}
],
"AdAvailOffset": 0,
"Inputs": [
{
"AudioSelectors": {
"Audio Selector 1": {
"Offset": 0,
"DefaultSelection": "DEFAULT",
"ProgramSelection": 1
}
},
"VideoSelector": {
"ColorSpace": "FOLLOW",
"Rotate": "DEGREE_0",
"AlphaBehavior": "DISCARD"
},
"FilterEnable": "AUTO",
"PsiControl": "USE_PSI",
"FilterStrength": 0,
"DeblockFilter": "DISABLED",
"DenoiseFilter": "DISABLED",
"InputScanType": "AUTO",
"TimecodeSource": "ZEROBASED",
"CaptionSelectors": {
"Captions Selector 1": {
"SourceSettings": {
"SourceType": "SRT",
"FileSourceSettings": {
"SourceFile": "s3://{{BUCKET-NAME}}/PROMO_CAP_01.srt"
}
}
}
},
"FileInput": "s3://{{BUCKET-NAME}}/PROMO_CAP_01.mp4"
}
]
},
"AccelerationSettings": {
"Mode": "DISABLED"
},
"StatusUpdateInterval": "SECONDS_60",
"Priority": 0
}
What I am missing?

Answer 1

According to the AWS Elemental MediaConvert user guide, SRT is not a supported output for a DASH-ISO output group when the input caption type is SRT.
Here's a link to that guide (reference page 176):
https://docs.aws.amazon.com/mediaconvert/latest/ug/mediaconvert-guide.pdf
The supported caption outputs for SRT input in DASH-ISO are:
Burn in
IMSC (as sidecar .fmp4)
IMSC (as sidecar .xml)
TTML (as sidecar .fmp4)
TTML (as sidecar .ttml)
Additionally, there is a gap in the documentation. SRT->DASH-ISO+WebVTT is supported, even though it is not listed. The documentation will be corrected, but I wanted to share that with you in case it helps.
If you must send SRT to the output destination, then you could create a separate output group where the caption is in a track with no container (see pages 192-196 in the document).