AWS MediaConvert and Alpha channels

Question

I'm trying to use AWS MediaConvert on a .mov file that has an alpha channel. I couldn't find a way to preserve the alpha channel. Seems like it's always discarded and I'm losing the transparency.
Even the input QuickTime settings have only two options - Discard and Remap to Luma which turns anything BUT the alpha channel to white (?!).

Any help would be appreciated to preserve the alpha channel.

Thank you

{
  "Queue": "arn:aws:mediaconvert:us-east-1:xxx:queues/Default",
  "UserMetadata": {},
  "Role": "arn:aws:iam::xxx:role/service-role/MediaConvert_Default_Role",
  "Settings": {
    "TimecodeConfig": {
      "Source": "ZEROBASED"
    },
    "OutputGroups": [
      {
        "CustomName": "test vp9",
        "Name": "DASH ISO",
        "Outputs": [
          {
            "ContainerSettings": {
              "Container": "MPD"
            },
            "VideoDescription": {
              "CodecSettings": {
                "Codec": "VP9",
                "Vp9Settings": {
                  "RateControlMode": "VBR",
                  "Bitrate": 1000000
                }
              }
            },
            "NameModifier": "_output1"
          }
        ],
        "OutputGroupSettings": {
          "Type": "DASH_ISO_GROUP_SETTINGS",
          "DashIsoGroupSettings": {
            "SegmentLength": 30,
            "Destination": "s3://xxx/",
            "FragmentLength": 2
          }
        }
      }
    ],
    "Inputs": [
      {
        "VideoSelector": {
          "AlphaBehavior": "DISCARD"
        },
        "TimecodeSource": "ZEROBASED",
        "FileInput": "https://xxx/yyy.mov"
      }
    ]
  },
  "AccelerationSettings": {
    "Mode": "DISABLED"
  },
  "StatusUpdateInterval": "SECONDS_60",
  "Priority": 0
}

score 1 · Answer 1 · answered May 25 '22 at 18:26

Thanks for your message. Regarding inputs with an alpha channel: The two supported formats are PNG stills with alpha OR a quicktime mov file using QTRLE Codec with alpha (RGBA). Other Quicktime codecs will fail. A mov using the animation codec content without alpha (only RGB) will fail.

Using either of the formats mentioned above, then positioning your overlay object correctly on the output canvas, should get you a properly keyed overlay. Preserving the alpha on output will require a target output format which supports alpha. I hope that helps.

AWS MediaConvert and Alpha channels

1 Answers1