diff options
Diffstat (limited to 'v4l2-mfc-encoder/README.txt')
| -rw-r--r-- | v4l2-mfc-encoder/README.txt | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/v4l2-mfc-encoder/README.txt b/v4l2-mfc-encoder/README.txt new file mode 100644 index 0000000..9b0f107 --- /dev/null +++ b/v4l2-mfc-encoder/README.txt @@ -0,0 +1,153 @@ +V4L2 Codec encoding example application +by Andrzej Hajda <a.hajda@samsung.com> + +=========== +* License * +=========== +Copyright 2012 Samsung Electronics Co., Ltd. + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + +http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. + +============= +* About MFC * +============= + +MFC stands for Multi Format Codec. It is a hardware module available in the +Exynos family of SoCs. It is capable of decoding a range of compressed +streams with resolution up to 1080p at 30 fps. This includes H264, H264, +MPEG1, MPEG2, MPEG4 and VC1. It also supports encoding in H264 and H263 format +up to 1080p and MPEG up to D1 resolution. + +============== +* About FIMC * +============== + +Although this is the example application for MFC it also uses the FIMC camera +module. + +======================= +* About the interface * +======================= + +The interface used by the MFC 5.1 driver is the Video4Linux2 framework. +It acts as a memory to memory device. It supports up to 16 contexts, each of +them can be setup to do encoding or decoding. + +========================= +* About the application * +========================= + +The purpose of this applications is to present and explain the usage of hardware +video codecs with the V4L2 interface. Application also presents usage of poll +interface with V4L2 devices as an alternative to threads. + +================================= +* Encoding in a few words * +================================= + +MFC codec is a memory to memory V4L2 device. Following steps should be performed +to encode video stream: +1. Open device. +2. Set image size and format on OUTPUT. MFC supports V4L2_PIX_FMT_NV12M format + with bytes per line aligned to 128 and image size aligned to 2048. +3. Set codec and buffer size on CAPTURE. Size should be not greater than 2MB. + Supported codecs: MPEG4, H263, H264. +4. Optionally set additional parameters (bitrate, fps,....). +5. Request CAPTURE and OUTPUT buffers. Due to hardware limitations of MFC on + some platforms it is recommended to use V4L2_MEMORY_MMAP buffers. +6. Enqueue CAPTURE buffers. +7. Enqueue OUTPUT buffer with first frame. +8. Start streaming (VIDIOC_STREAMON) on both ends. +9. Simultaneously: + - enqueue buffers with next frames, + - dequeue used OUTPUT buffers (blocking operation), + - dequeue buffers with encoded stream (blocking operation), + - enqueue free CAPTURE buffers. +10. Last frame should have set flags field to V4L2_BUF_FLAG_LAST to + inform codec about the end of the stream. +11. Stop dequeuing CAPTURE frames after dequeuing frame with luma plane + bytesused equal 0. +12. Stop streaming (VIDIOC_STREAMOFF) on both ends. +13. Close device. + +Encoded stream is in elementary stream format. + +============================== +* Application in a few words * +============================== + +The application uses pattern of device chain. Single device has input and output. +Chained devices have connected output of one device with input of the following +device. Devices uses buffers to pass data between them. + +Video4Linux2 devices uses this pattern natively. The application uses also this +pattern for pseudo devices: + in_demo - input device providing stream of NV12M frames with animation of + white square flying over 'noisy background'. + out_file - writes incoming data to file. + +Application uses following strategy regarding queuing buffers: +1. At the beginning all buffers are enqueued in output queues of devices. +2. Every time buffer is dequeued from out queue it is immediately enqueued + in the input queue of the next device. +3. Every time buffer is dequeued from input queue it is immediately enqueued + in the output queue of the previous device. + +Application uses poll interface to wait for devices which can be dequeued +without blocking. When device is ready dequeue/enqueue operation is performed. + +There are two types of devices: +1. V4L2 devices: + - mfc, + - in_camera. +2. Function devices - they use read or write function to pass data: + - in_demo, + - out_file. + +Implementation of devices: mfc.c, in_camera.c, in.demo.c out_file.c shows that +extending application with new devices should be quite easy. + +=========================== +* Running the application * +=========================== + +The application takes a few necessary arguments. The only required argument is +MFC device (-m). + +Options: + -i <device> - FIMC camera device (e.g. /dev/video1) + If not specified demo input device is used + -m <device> - (required) MFC device (e.g. /dev/video8) + -o <file> - Output file name + -c <codec> - The codec of the encoded stream + Available codecs: mpeg4, h263, h264 + -d <duration> - Number of frames to encode + -r <rate> - Frame rate + -b <bitrate> - Bitrate + -s <size> - Size of frame in format WxH + +To determine which devices to use you can try the following commands. + +For MFC: +dmesg | grep -e s5p-mfc.*encoder.*/dev/video +which outputs: +[ 2.160683] s5p-mfc s5p-mfc: encoder registered as /dev/video9 + +For FIMC camera: +dmesg | grep -e fimc...capture.*/dev/video +which outputs: +[ 2.484000] s5p-fimc-md: Registered exynos4-fimc.0.capture as /dev/video1 +[ 2.497174] s5p-fimc-md: Registered exynos4-fimc.1.capture as /dev/video3 +[ 2.510368] s5p-fimc-md: Registered exynos4-fimc.2.capture as /dev/video5 +[ 2.523578] s5p-fimc-md: Registered exynos4-fimc.3.capture as /dev/video7 + |