It helps to upload a high bitrate file. Ultimately, though, the uploaded file will be transcoded to low bitrate 8 bpc 4:2:0 video. The are a few practices within the workflow that can minimize potential problems. Note that some of the items listed below are overkill if the final output will only be viewed online:
– Your source material is 8 bpc YCC color. Maintain YCC color (Premiere Pro YUV) and/or a high bit depth through the pipeline (32 bpc in Premiere Pro, 16-32 bpc in After Effects). Check the icons for each effect to ensure they meet requirements. Many 8-bit effects have a higher bit-depth alternative that can achieve the same desired results.
– Minimize the possibility of banding by avoiding smooth gradients. Use stripes, textures, overlays, etc. to break-up large areas.
– Add grain to low movement backgrounds to avoid macroblocking. Note that the Noise effect in Premiere Pro is 8-bit, so you would need to encode an intermediate file with the noise to avoid adding an 8-bit effect to the main sequence.
– Use the color scopes in Premiere Pro to check for any potential issues.
– Minimize the number of intermediate file transfers across applications. Use dynamic links as long as your system isn’t getting bogged down. If an intermediate file is needed, select a 10-bit, 422/444, high bitrate, all-intraframe codec like ProRes, DNxHD, AVC-Intra, or, if storage space is not an issue, uncompressed V210 or DPX.
– If exporting to a 10-bit codec enable Maximum Bit Depth in the sequence and export settings, and set Depth to 48- or 64-bit (Premiere Pro) or “Trillions of Colors” (After Effects). Otherwise, the output will be 8-bit regardless of the codec.
– In Premiere Pro use the Export button instead of Queue. For H.264 from After Effects pull the file/composition into AME or Premiere Pro instead of exporting from the AE Render Queue.