[FAQ] TDA4VM: What parameters in the VPU driver are used for setting I-frame and IDR key-frame period?

As of the 8.6 SDK, the Imagination VPU GStreamer to V4L2 controls were not enabled and only were enabled in 9.0. You can still enable I-frame period by hard-coding the parameters in the 8.6 version of the driver. The following modifications in the vxe_v4l2.c will set the I-frame/IDR period to 5.

•  In the vxe_s_ext_ctrls function under the V4L2_CID_MPEG_VIDEO_H264_I_PERIOD case, modify the ctx->rc.intra_freq = 5 and ctx->vparams.intra_cnt = 5 to make every 5 frames an I-frame:

static int vxe_s_ext_ctrls(struct file *file, void *priv,
			   struct v4l2_ext_controls *ctrls)
{
	struct vxe_enc_ctx *ctx = file2ctx(file);
	struct device *dev = ctx->dev->dev;
	int i;
	int ret;

	ctrls->reserved[0] = 0;
	ctrls->reserved[1] = 0;

	if (ctrls->which != V4L2_CTRL_WHICH_CUR_VAL)
		return -EINVAL;

	/* Verify first with try_ext_ctrls */
	ret = vxe_try_ext_ctrls(file, priv, ctrls);
	if (ret) {
		/* Indicate verification stage error */
		ctrls->error_idx = ctrls->count;
		return ret;
	}

	/* Set all values in this set of commands */
	for (i = 0; i < ctrls->count; i++) {
		ctrls->controls[i].reserved2[0] = 0;

		switch (ctrls->controls[i].id) {
		case V4L2_CID_MPEG_VIDEO_GOP_SIZE:
			ctrls->controls[i].size = 0;
			ctx->vparams.idr_period = 5;
			break;
		case V4L2_CID_MPEG_VIDEO_BITRATE:
			ctrls->controls[i].size = 0;
			ctx->rc.bits_per_second = ctrls->controls[i].value;
			break;
		case V4L2_CID_MPEG_VIDEO_H264_I_PERIOD:
			ctrls->controls[i].size = 0;
			ctx->rc.intra_freq = 5;
			ctx->vparams.intra_cnt = 5;
			break;
		default:
			dev_err(dev, "%s Invalid control id %#08x\n",
				__func__, ctrls->controls[i].id);
			ctrls->error_idx = i;
			return -EINVAL;
		}
	}

	return 0;
}

• To set the IDR key-frame period you will set both the above parameters and the GOP with ctx->vparams.idr_period = 5 under V4L2_CID_MPEG_VIDEO_GOP_SIZE  to make every 5 frames a key-frame.

Since the userspace API is not implemented correctly to be controlled by GStreamer in the 5.10 (8.6 SDK) kernel. I will attach the patch that was made in the 6.1 (9.0 SDK) kernel which added this implementation to set V4L2 controls from GStreamer below:

0268.tiL6.1-1-2-media-img-vxe-vxd-enable-GStreamer-1.20.5.patch

With this patch you should be able to avoid hard-coding and the values in the driver and just use the GStreamer pipeline's plugins. However since this patch was implemented on a newer kernel TI is uncertain about what (if any) back-porting efforts are involved.

Best Regards,
Sarabesh S.