mirror of
https://github.com/espressif/esp-idf.git
synced 2026-10-01 18:50:34 +03:00
docs(dma2d): added async color convert programming guide
This commit is contained in:
morris
@@ -0,0 +1,295 @@
|
||||
=============================
|
||||
Asynchronous Color Conversion
|
||||
=============================
|
||||
|
||||
:link_to_translation:`zh_CN:[中文]`
|
||||
|
||||
This document introduces the Async Color Convert driver in ESP-IDF. The table of contents is as follows:
|
||||
|
||||
.. contents::
|
||||
:local:
|
||||
:depth: 2
|
||||
|
||||
Overview
|
||||
========
|
||||
|
||||
{IDF_TARGET_NAME} provides a DMA2D engine that can offload 2D copy and color conversion work from the CPU.
|
||||
|
||||
This driver is useful when your application needs to:
|
||||
|
||||
- convert an image from one pixel format to another
|
||||
- copy only a window of a larger image
|
||||
- queue multiple conversions without doing the work on the CPU
|
||||
- move between RGB and UYVY formats while selecting the RGB/YUV conversion standard
|
||||
|
||||
The Async Color Convert driver wraps DMA2D request preparation, queueing, and completion handling into a small API that supports both:
|
||||
|
||||
- asynchronous submission with an ISR callback
|
||||
- a simpler blocking API built on top of the same request path
|
||||
|
||||
Quick Start
|
||||
===========
|
||||
|
||||
If you are new to this driver, start with the simplest workflow:
|
||||
|
||||
1. Install the driver
|
||||
2. Prepare one :cpp:type:`async_color_convert_request_t`
|
||||
3. Submit the conversion through either the blocking or non-blocking API
|
||||
4. Consume the converted output buffer after the conversion completes
|
||||
5. Either submit another request or uninstall the driver when finished
|
||||
|
||||
The typical usage flow is:
|
||||
|
||||
.. mermaid::
|
||||
|
||||
flowchart TD
|
||||
install["Install driver<br/>esp_async_color_convert_install_dma2d"] --> request["Prepare request<br/>async_color_convert_request_t"]
|
||||
request --> blocking["Blocking path<br/>esp_color_convert_blocking"]
|
||||
request --> nonBlocking["Non-blocking path<br/>esp_async_color_convert"]
|
||||
nonBlocking --> callback["Wait for callback or task notification"]
|
||||
blocking --> result["Use converted buffer"]
|
||||
callback --> result
|
||||
result --> request
|
||||
result --> uninstall["Optional cleanup<br/>esp_async_color_convert_uninstall"]
|
||||
|
||||
Scenario 1: Start with One Blocking Conversion
|
||||
==============================================
|
||||
|
||||
The easiest way to learn the API is to convert one image and wait until the conversion is complete.
|
||||
|
||||
The following flow mirrors the :example:`peripherals/dma/async_color_convert` example. It converts one embedded UYVY422 image into BGR24 and then lets the application consume the converted output:
|
||||
|
||||
.. code:: c
|
||||
|
||||
async_color_convert_handle_t conv_hdl = NULL; // Driver handle returned by the install API
|
||||
async_color_convert_config_t config = {
|
||||
.backlog = 1, // One in-flight request is enough for this simple blocking example
|
||||
.dma_burst_size = 16, // Start with the default burst size used by the example
|
||||
};
|
||||
// Create one Async Color Convert driver instance backed by DMA2D.
|
||||
ESP_ERROR_CHECK(esp_async_color_convert_install_dma2d(&config, &conv_hdl));
|
||||
|
||||
async_color_convert_request_t req = {
|
||||
.src_buffer = sample_96x64_uyvy_yuv_start, // Source image can be in flash or RAM, as long as DMA can access it
|
||||
.src_stride = 96, // Source image row stride, in pixels
|
||||
.src_height = 64, // Source image height, in pixels
|
||||
.src_x = 0, // Start from the left edge of the source image
|
||||
.src_y = 0,
|
||||
.dst_buffer = dst_bgr, // Destination buffer in DMA-capable RAM
|
||||
.dst_stride = 96, // Destination image row stride, in pixels
|
||||
.dst_height = 64, // Destination image height, in pixels
|
||||
.dst_x = 0, // Write the converted output from the top-left corner
|
||||
.dst_y = 0,
|
||||
.copy_width = 96, // Convert the full image width, in pixels
|
||||
.copy_height = 64, // Convert the full image height, in pixels
|
||||
.src_color_format = ESP_COLOR_FOURCC_UYVY, // Source pixels are UYVY422
|
||||
.dst_color_format = ESP_COLOR_FOURCC_BGR24, // Destination pixels are BGR24 (used as RGB888 in this driver)
|
||||
.color_conv_std = COLOR_CONV_STD_RGB_YUV_BT601, // RGB/YUV standard used for this conversion pair
|
||||
};
|
||||
|
||||
// Wait until DMA2D finishes the conversion. -1 means wait forever.
|
||||
ESP_ERROR_CHECK(esp_color_convert_blocking(conv_hdl, &req, -1));
|
||||
|
||||
// Release the driver after all conversions are done.
|
||||
ESP_ERROR_CHECK(esp_async_color_convert_uninstall(conv_hdl));
|
||||
|
||||
This flow introduces the most important ideas:
|
||||
|
||||
- :cpp:func:`esp_async_color_convert_install_dma2d` creates the driver instance
|
||||
- :cpp:type:`async_color_convert_request_t` describes the source image, destination image, and conversion window
|
||||
- :cpp:func:`esp_color_convert_blocking` waits until the hardware finishes the conversion
|
||||
- :cpp:func:`esp_async_color_convert_uninstall` releases the driver resources
|
||||
|
||||
For the blocking API, ``timeout_ms = -1`` means wait forever. Other timeout values are currently unsupported and return ``ESP_ERR_INVALID_ARG``.
|
||||
|
||||
Understanding ``async_color_convert_request_t``
|
||||
-----------------------------------------------
|
||||
|
||||
Most application issues come from building the request incorrectly, so it is worth understanding the structure carefully.
|
||||
|
||||
.. important::
|
||||
|
||||
In :cpp:type:`async_color_convert_request_t`, all geometry fields are measured in **pixels**, not bytes. This includes ``src_stride``, ``src_height``, ``src_x``, ``src_y``, ``dst_stride``, ``dst_height``, ``dst_x``, ``dst_y``, ``copy_width``, and ``copy_height``.
|
||||
|
||||
``src_stride`` and ``dst_stride`` are row strides, not conversion widths. They describe how many pixels each full image row spans in memory, so they can be larger than ``copy_width`` when converting a window inside a larger image.
|
||||
|
||||
The structure describes two things at the same time:
|
||||
|
||||
- the full source and destination images in memory
|
||||
- the rectangular window that should be converted
|
||||
|
||||
The key fields are:
|
||||
|
||||
- :cpp:member:`async_color_convert_request_t::src_buffer`
|
||||
Base address of the source image
|
||||
- :cpp:member:`async_color_convert_request_t::src_stride`
|
||||
Source image row stride in pixels
|
||||
- :cpp:member:`async_color_convert_request_t::src_height`
|
||||
Source image height in pixels
|
||||
- :cpp:member:`async_color_convert_request_t::src_x` and :cpp:member:`async_color_convert_request_t::src_y`
|
||||
Top-left corner of the source window
|
||||
- :cpp:member:`async_color_convert_request_t::dst_buffer`
|
||||
Base address of the destination image
|
||||
- :cpp:member:`async_color_convert_request_t::dst_stride`
|
||||
Destination image row stride in pixels
|
||||
- :cpp:member:`async_color_convert_request_t::dst_height`
|
||||
Destination image height in pixels
|
||||
- :cpp:member:`async_color_convert_request_t::dst_x` and :cpp:member:`async_color_convert_request_t::dst_y`
|
||||
Top-left corner of where the converted window should be written
|
||||
- :cpp:member:`async_color_convert_request_t::copy_width` and :cpp:member:`async_color_convert_request_t::copy_height`
|
||||
Size of the rectangle to convert
|
||||
- :cpp:member:`async_color_convert_request_t::src_color_format` and :cpp:member:`async_color_convert_request_t::dst_color_format`
|
||||
Source and destination pixel formats
|
||||
- :cpp:member:`async_color_convert_request_t::color_conv_std`
|
||||
RGB/YUV conversion standard, used for RGB <-> YUV conversions
|
||||
|
||||
Both the source window and destination window must stay within the bounds of their corresponding images.
|
||||
|
||||
Supported Conversions
|
||||
---------------------
|
||||
|
||||
The following format pairs are supported by this driver:
|
||||
|
||||
.. list-table::
|
||||
:header-rows: 1
|
||||
|
||||
* - Source format
|
||||
- Destination format
|
||||
- Conversion standard
|
||||
* - same as destination (skip conversion)
|
||||
- same as source (skip conversion)
|
||||
- N/A
|
||||
* - RGB565
|
||||
- RGB888
|
||||
- N/A
|
||||
* - RGB888
|
||||
- RGB565
|
||||
- N/A
|
||||
* - RGB888
|
||||
- UYVY422
|
||||
- BT.601
|
||||
* - RGB888
|
||||
- UYVY422
|
||||
- BT.709
|
||||
* - UYVY422
|
||||
- RGB888
|
||||
- BT.601
|
||||
* - UYVY422
|
||||
- RGB888
|
||||
- BT.709
|
||||
|
||||
.. note::
|
||||
|
||||
In this driver, RGB888 uses ``ESP_COLOR_FOURCC_BGR24`` and UYVY422 uses ``ESP_COLOR_FOURCC_UYVY``.
|
||||
|
||||
Always set :cpp:member:`async_color_convert_request_t::src_color_format` and
|
||||
:cpp:member:`async_color_convert_request_t::dst_color_format`.
|
||||
Set :cpp:member:`async_color_convert_request_t::color_conv_std` when converting between RGB and YUV.
|
||||
|
||||
Scenario 2: Use the Asynchronous API with a Callback
|
||||
====================================================
|
||||
|
||||
Once the blocking flow is clear, the next step is to queue a request and let the driver notify you from interrupt context when it is finished.
|
||||
|
||||
.. code:: c
|
||||
|
||||
static bool color_conv_done_cb(async_color_convert_handle_t conv_hdl,
|
||||
async_color_convert_event_data_t *edata,
|
||||
void *cb_args)
|
||||
{
|
||||
BaseType_t high_task_wakeup = pdFALSE; // Required by FreeRTOS when an ISR wakes a task
|
||||
SemaphoreHandle_t sem = (SemaphoreHandle_t)cb_args; // User context passed at submit time
|
||||
// Notify a waiting task that the conversion has finished.
|
||||
xSemaphoreGiveFromISR(sem, &high_task_wakeup);
|
||||
// Return true when the unblocked task should run immediately after the ISR.
|
||||
return high_task_wakeup == pdTRUE;
|
||||
}
|
||||
|
||||
async_color_convert_request_t req = {
|
||||
.src_buffer = src_buf, // Source image base address
|
||||
.src_stride = src_width, // Source image row stride, in pixels
|
||||
.src_height = src_height,
|
||||
.src_x = 0,
|
||||
.src_y = 0,
|
||||
.dst_buffer = dst_buf, // Destination image base address
|
||||
.dst_stride = dst_width, // Destination image row stride, in pixels
|
||||
.dst_height = dst_height,
|
||||
.dst_x = 0,
|
||||
.dst_y = 0,
|
||||
.copy_width = copy_width,
|
||||
.copy_height = copy_height,
|
||||
.src_color_format = ESP_COLOR_FOURCC_RGB16,
|
||||
.dst_color_format = ESP_COLOR_FOURCC_BGR24,
|
||||
};
|
||||
|
||||
// Queue one asynchronous request. The callback runs later in ISR context.
|
||||
ESP_ERROR_CHECK(esp_async_color_convert(conv_hdl, &req, color_conv_done_cb, sem));
|
||||
// Wait in task context until the callback gives the semaphore.
|
||||
xSemaphoreTake(sem, portMAX_DELAY);
|
||||
|
||||
The callback runs in ISR context, so keep it short and only use ISR-safe APIs such as ``xSemaphoreGiveFromISR`` or ``xQueueSendFromISR``.
|
||||
|
||||
Operational Notes
|
||||
=================
|
||||
|
||||
Driver Configuration
|
||||
--------------------
|
||||
|
||||
The driver configuration fields are:
|
||||
|
||||
- :cpp:member:`async_color_convert_config_t::backlog`
|
||||
Maximum number of in-flight or pending requests. ``0`` uses a driver default.
|
||||
- :cpp:member:`async_color_convert_config_t::dma_burst_size`
|
||||
DMA burst size in bytes. ``0`` uses a driver default.
|
||||
- :cpp:member:`async_color_convert_config_t::intr_priority`
|
||||
DMA2D interrupt priority. ``0`` uses the default low/medium priority.
|
||||
|
||||
DMA Burst Size
|
||||
--------------
|
||||
|
||||
The ``dma_burst_size`` affects DMA transfer efficiency:
|
||||
|
||||
- Larger burst sizes may improve throughput
|
||||
- Larger burst sizes can also increase bus occupancy, so they are not always best for every workload
|
||||
- Common starting values are 16, 32, and 64 bytes
|
||||
|
||||
The best value depends on the chip's DMA controller capabilities and how much memory bandwidth is shared with other active components in the system.
|
||||
|
||||
Thread Safety and ISR Rules
|
||||
---------------------------
|
||||
|
||||
- The driver is thread-safe. Requests from different tasks are serialized through the internal queue.
|
||||
- :cpp:func:`esp_async_color_convert` can be called from tasks to enqueue requests.
|
||||
- The callback type :cpp:type:`async_color_convert_isr_cb_t` runs in ISR context.
|
||||
- Do not call blocking APIs from the callback.
|
||||
- :cpp:func:`esp_color_convert_blocking` must not be called from ISR context.
|
||||
|
||||
Uninstalling the Driver
|
||||
-----------------------
|
||||
|
||||
When the driver is no longer needed:
|
||||
|
||||
.. code:: c
|
||||
|
||||
// Uninstall only after all queued conversions have completed.
|
||||
ESP_ERROR_CHECK(esp_async_color_convert_uninstall(conv_hdl));
|
||||
|
||||
If requests are still pending, :cpp:func:`esp_async_color_convert_uninstall` returns :c:macro:`ESP_ERR_INVALID_STATE`.
|
||||
|
||||
Application Example
|
||||
===================
|
||||
|
||||
- :example:`peripherals/dma/async_color_convert` shows a beginner-friendly blocking conversion flow:
|
||||
|
||||
- an embedded ``.yuv`` image is read directly from mapped flash
|
||||
- DMA2D converts the image from UYVY422 to BGR24
|
||||
- the converted output is base64-encoded and printed to the console
|
||||
- pytest reconstructs the image as a PNG artifact and compares it against a golden reference image
|
||||
|
||||
API Reference
|
||||
=============
|
||||
|
||||
Async Color Convert Driver Functions
|
||||
------------------------------------
|
||||
|
||||
.. include-build-file:: inc/esp_async_color_convert.inc
|
||||
@@ -1,5 +1,5 @@
|
||||
============================
|
||||
Asynchronous CRC (Async CRC)
|
||||
Asynchronous CRC Calculation
|
||||
============================
|
||||
|
||||
:link_to_translation:`zh_CN:[中文]`
|
||||
|
||||
@@ -9,6 +9,7 @@ Peripherals API
|
||||
:SOC_ADC_SUPPORTED: adc/index
|
||||
:SOC_ANA_CMPR_SUPPORTED: ana_cmpr
|
||||
:SOC_GDMA_SUPPORT_CRC: async_crc
|
||||
:SOC_DMA2D_SUPPORTED: async_color_convert
|
||||
:SOC_ASYNC_MEMCPY_SUPPORTED: async_memcpy
|
||||
:SOC_BITSCRAMBLER_SUPPORTED: bitscrambler
|
||||
:SOC_MIPI_CSI_SUPPORTED: camera_driver
|
||||
|
||||
Reference in New Issue
Block a user