Re: [PATCH v2 2/2] media: iris: disable time-delta-based rate control for VBR

[Vikash Garodia <vikash.garodia@oss.qualcomm.com>]

On 7/10/2026 8:24 AM, Vishnu Reddy wrote:
> From: Gourav Kumar<gouravk@qti.qualcomm.com>
> 
> The iris encoder driver was not sending
> HFI_PROP_TIME_DELTA_BASED_RATE_CONTROL to the firmware during encoder
> initialization. Without this property, the firmware defaults to
> time-delta-based rate control (enabled), which calculates the output
> bitrate from actual frame timing rather than following the configured
> bitrate target.
> This caused variable bitrate (VBR) encoding to produce ~5x configured
> bitrate. For example, with video_bitrate=896000 (896 Kbps), the output
> is ~4.4 Mbps instead of the expected ~896 Kbps.
> Time-delta-based rate control is designed for variable frame rate (VFR)
> scenarios where the encoder adapts to actual frame timing. However, when
> an application explicitly configures a bitrate target, the firmware must
> follow that target regardless of frame timing.
> Fix this by adding the TIME_DELTA_BASED_RC capability with a default value
> of 0 (disabled) and sending HFI_PROP_TIME_DELTA_BASED_RATE_CONTROL = 0 to
> the firmware during stream-on, allowing the firmware to use the configured
> bitrate as the target.
> 
> Signed-off-by: Gourav Kumar<gouravk@qti.qualcomm.com>
> Signed-off-by: Vishnu Reddy<busanna.reddy@oss.qualcomm.com>
> ---
>   drivers/media/platform/qcom/iris/iris_ctrls.c         | 19 +++++++++++++++++++
>   drivers/media/platform/qcom/iris/iris_ctrls.h         |  1 +
>   drivers/media/platform/qcom/iris/iris_hfi_gen2.c      | 10 ++++++++++
>   .../media/platform/qcom/iris/iris_hfi_gen2_defines.h  |  1 +
>   .../media/platform/qcom/iris/iris_platform_common.h   |  1 +
>   5 files changed, 32 insertions(+)

Reviewed-by: Vikash Garodia <vikash.garodia@oss.qualcomm.com>