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

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

On 7/7/2026 12:05 PM, 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.
> 

same here, we can drop the new empty lines

> 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(+)
> 
> diff --git a/drivers/media/platform/qcom/iris/iris_ctrls.c b/drivers/media/platform/qcom/iris/iris_ctrls.c
> index 10e33b8a73f6..f6136e655b98 100644
> --- a/drivers/media/platform/qcom/iris/iris_ctrls.c
> +++ b/drivers/media/platform/qcom/iris/iris_ctrls.c
> @@ -1477,6 +1477,25 @@ int iris_set_layer_bitrate(struct iris_inst *inst, enum platform_inst_fw_cap_typ
>   					     &bitrate, sizeof(u32));
>   }
>   
> +int iris_set_time_delta_based_rc(struct iris_inst *inst, enum platform_inst_fw_cap_type cap_id)
> +{
> +	const struct iris_hfi_session_ops *hfi_ops = inst->hfi_session_ops;
> +	u32 hfi_id = inst->fw_caps[cap_id].hfi_id;
> +	u32 value = inst->fw_caps[cap_id].value;
> +
> +	/*
> +	 * Disable time-delta-based rate control (value = 0).
> +	 * This overrides the firmware's default (enabled), ensuring the
> +	 * firmware uses the configured bitrate target rather than calculating
> +	 * bitrate from frame timing.
> +	 */
> +	return hfi_ops->session_set_property(inst, hfi_id,
> +					     HFI_HOST_FLAGS_NONE,
> +					     iris_get_port_info(inst, cap_id),
> +					     HFI_PAYLOAD_U32,
> +					     &value, sizeof(u32));
> +}
> +
>   int iris_set_properties(struct iris_inst *inst, u32 plane)
>   {
>   	const struct iris_hfi_session_ops *hfi_ops = inst->hfi_session_ops;
> diff --git a/drivers/media/platform/qcom/iris/iris_ctrls.h b/drivers/media/platform/qcom/iris/iris_ctrls.h
> index 3c462ec9190b..10e046722ad3 100644
> --- a/drivers/media/platform/qcom/iris/iris_ctrls.h
> +++ b/drivers/media/platform/qcom/iris/iris_ctrls.h
> @@ -47,6 +47,7 @@ int iris_set_layer_type(struct iris_inst *inst, enum platform_inst_fw_cap_type c
>   int iris_set_layer_count_gen1(struct iris_inst *inst, enum platform_inst_fw_cap_type cap_id);
>   int iris_set_layer_count_gen2(struct iris_inst *inst, enum platform_inst_fw_cap_type cap_id);
>   int iris_set_layer_bitrate(struct iris_inst *inst, enum platform_inst_fw_cap_type cap_id);
> +int iris_set_time_delta_based_rc(struct iris_inst *inst, enum platform_inst_fw_cap_type cap_id);
>   int iris_set_properties(struct iris_inst *inst, u32 plane);
>   
>   #endif
> diff --git a/drivers/media/platform/qcom/iris/iris_hfi_gen2.c b/drivers/media/platform/qcom/iris/iris_hfi_gen2.c
> index acc0ed8adda1..d119ad599c31 100644
> --- a/drivers/media/platform/qcom/iris/iris_hfi_gen2.c
> +++ b/drivers/media/platform/qcom/iris/iris_hfi_gen2.c
> @@ -416,6 +416,16 @@ static const struct platform_inst_fw_cap inst_fw_cap_sm8550_enc[] = {

targets other than the one using inst_fw_cap_sm8550_enc ?


>   		.flags = CAP_FLAG_OUTPUT_PORT | CAP_FLAG_MENU,
>   		.set = iris_set_bitrate_mode_gen2,
>   	},
> +	{
> +		.cap_id = TIME_DELTA_BASED_RC,
> +		.min = 0,
> +		.max = 1,
> +		.step_or_mask = 1,
> +		.value = 0,
> +		.hfi_id = HFI_PROP_TIME_DELTA_BASED_RATE_CONTROL,
> +		.flags = CAP_FLAG_OUTPUT_PORT,
> +		.set = iris_set_time_delta_based_rc,
> +	},
>   	{
>   		.cap_id = FRAME_SKIP_MODE,
>   		.min = V4L2_MPEG_VIDEO_FRAME_SKIP_MODE_DISABLED,
> diff --git a/drivers/media/platform/qcom/iris/iris_hfi_gen2_defines.h b/drivers/media/platform/qcom/iris/iris_hfi_gen2_defines.h
> index 776b21cd11b2..8766d9e49611 100644
> --- a/drivers/media/platform/qcom/iris/iris_hfi_gen2_defines.h
> +++ b/drivers/media/platform/qcom/iris/iris_hfi_gen2_defines.h
> @@ -67,6 +67,7 @@ enum hfi_rate_control {
>   };
>   
>   #define HFI_PROP_RATE_CONTROL			0x0300012a
> +#define HFI_PROP_TIME_DELTA_BASED_RATE_CONTROL	0x0300012b
>   #define HFI_PROP_QP_PACKED			0x0300012e
>   #define HFI_PROP_MIN_QP_PACKED			0x0300012f
>   #define HFI_PROP_MAX_QP_PACKED			0x03000130
> diff --git a/drivers/media/platform/qcom/iris/iris_platform_common.h b/drivers/media/platform/qcom/iris/iris_platform_common.h
> index c9256f2323dc..99dc6d5c72ba 100644
> --- a/drivers/media/platform/qcom/iris/iris_platform_common.h
> +++ b/drivers/media/platform/qcom/iris/iris_platform_common.h
> @@ -183,6 +183,7 @@ enum platform_inst_fw_cap_type {
>   	LAYER3_BITRATE_HEVC,
>   	LAYER4_BITRATE_HEVC,
>   	LAYER5_BITRATE_HEVC,
> +	TIME_DELTA_BASED_RC,
>   	INST_FW_CAP_MAX,
>   };
>   
> 

Regards,
Vikash