AV1 encoder - unexpected 44 byte header at start of encoded bitstream

[oviano]

I am using the v4l2 API to encode with AV1, similar to the examples.

I have noticed that in comparison to when I encode with AV1 on the desktop Video Codec, with the Jetson Multimedia API I get this strange header at the start.

I am using DAV1D to decode, and it falls down trying to parse from the start as the 44 byte header is obviously not a valid part of the bitstream.

I’m not too sure exactly where it is coming from, or what is for, and certainly apps like VLC, or the browser-based parser (see below) are able to skip it, so I’m wondering if anyone can shed some light on what it is or how I can get rid of it, or is it always 44 bytes so I can just skip it?

As can be seen in the HEX in the screenshot below, it includes the string “AV01” so it must be some kind of header information?

As I mentioned, the Video Codec SDK doesn’t have this header, so DAV1D can decode from the start of the stream.

[oviano]

Ok it looks like it must be adding IVF headers by default, so I guess I need to find the flag to turn that off.

[oviano]

As per this post Disabling IVF headers on a VP8 stream the documentation is similarly misleading for AV1.

For V4L2_CID_MPEG_VIDEOENC_AV1_HEADERS_WITH_FRAME it states:

/**

• Control ID to enable/disable setting for attaching IVF headers.

• Only to be used for AV1 codec.

• A boolean value should be supplied with this control.

• If value is false headers will be disabled and true will enable the headers.

• @attention This control should be set after setting formats on both the planes

• and before requesting buffers on either plane.

*/

define V4L2_CID_MPEG_VIDEOENC_AV1_HEADERS_WITH_FRAME (V4L2_CID_MPEG_BASE+569)

However, it only works if the flag is set after setting the capture format but before the output format.