Hi, I am having issues rendering videos to Nvidia AV1/MP4 using Voukoder Pro.
Even though I set the Movflags to Faststart, this setting doesn't seem to affect the render in Adobe Premiere.
After render I don't get the usual extra delay while the atom is moved, nor does FFMPEG see the moov atom moved to the front.
Is that a limitation of AV1 encoding? Or did I just forget to change any additional settings required? Never had this issue when using h.264 before. 
It depends on the implementation.
ChatGPT explains it like this:
Yes, technically: The MP4 container supports AV1 using the AV1 ISO-BMFF format, and tools like FFmpeg can place the moov atom at the beginning even for AV1.
However, support depends on the muxer and player:
- FFmpeg with -movflags +faststart works, but you must use libaom, libsvtav1, or other AV1 encoders that output compatible streams.
- The AV1 stream must be correctly formatted according to the AV1 codec ISO Media File Format Binding specification (ISO/IEC 14496-15:2017 + amendments).
- Some older players or browsers may not fully support AV1-in-MP4 yet, especially for streaming.
