文件列表:

LICENSE (1065, 2016-10-18)
result (0, 2016-10-18)
result\ldpcsnr3.jpg (191607, 2016-10-18)
src (0, 2016-10-18)
src\bit2pic.m (412, 2016-10-18)
src\decoder.mexa64 (16662, 2016-10-18)
src\decoder.mexmaci64 (18460, 2016-10-18)
src\decoder.mexw64 (12288, 2016-10-18)
src\encoder.mexa64 (1498396, 2016-10-18)
src\encoder.mexmaci64 (1500176, 2016-10-18)
src\encoder.mexw64 (1496576, 2016-10-18)
src\load_video.m (2107, 2016-10-18)
src\pic2bit.m (334, 2016-10-18)
src\show_pic_ber.fig (47846, 2016-10-18)
src\show_pic_ber.m (9544, 2016-10-18)
testcase (0, 2016-10-18)
testcase\sample.avi (375688, 2016-10-18)

# Intro For many days, I was wandering the physical meaning of BER (bit-error rate) and SNR (signal to noise ratio), which are heavily used by designers in communication domain. Besides, the effectness of ECC (error correction code) was far from illustrative. Therefore I built this task (in Matlab and C) to monitor the physical meaning of SNR, BER, ECC (LDPC), illustrated in the context of (Image) video transmission. # System discription The Matlab GUI simulates video transmission via a gaussian noise (AWG) channel. The modulation sheme is QPSK. For error correction, a LDPC decoder is utilized. To speedup the simulation, the model uses a custumized LDPC encoder/decoder, rather than the built in one form communication_toolbox. This brings ~100 speedup. The LDPC encoder/decoder is compatible to IEEE 802.11ad starndrd, by default it is in 1/2 coding rate, you can hack it to use 5/8, 3/4, or 13/16 coding rate. The block size of the code is fixed to be 672 bits. It takes logrithmetic input from the mapper. The LDPC decoder is implemented in fixed-point to represent industrial chip behavior. The bitwidth is between 4-10. Currently we only provide mex code to be used in Matlab. The original c code, as well as the exact bitwidth, are still confidential. We hope to open-source to the public soon. User can choose input video_file, as well as the SNR to simulate. A sample result might be found in /result/ldpcsnr3.jpg.  # User's guide ## system requirements * ***-bit operating system of ethier Windows, Unix, or MAC OSX * ***-bit Matlab, with licences of: * basic Matlab license * communication_toolbox * signal_toolbox ## Usage guide ### Download this git page Otherwise, you can simply fork this page by: ```bash git clone https://github.com/yanxianghuang/video_ldpc ``` ### Run the script from Matlab: Open Matlab, entering the src folder, start the program by typing ```Matlab show_pic_ber ``` in your Matlab commandline. A figure template should appear. Adjust the parameters in the right-top corner __Panel__: * select file for testcase, you can choose the one in '../testcase/sample.avi'; * choose the SNR value in dB for simulation, preferably chose 3; * for 'start from' item item, you may choose 0, meaning we start from the first frame (the 0 second). * tick the Updating new frames, if you want the simulation process to update new frames automatically (streaming). * click Simulate, you are ready to see the effect, of the original frame(s), corrupted by the signal frame(s), and the decoded form error correction code frame(s). * To stop, untick the 'updating new frame', it will stop when finishs current frame. To start a new simulation, click Simulate button. Be patient as the simulation may take long. This is mainly due to the time-consuming demapper function from communication_toolbox. I hope one day I'll find the time to convert it to Python, or reuse my own demapping, for speed-up. Enjoy, and if you have and suggestions, please shot. # hacker's guide You can modify the program as you like. For instance, you can change the modulation scheme, channel noise model, LDPC schemes (or even substitute it with one you have). ## File structure * src * show_pic_ber.m (the main function) * show_pic_ber.fig (the GUI interface, it will be open once show_pic_ber.m is used) * load_video.m (loading video function/script) * pic2bit.m (function: convert picture/frame into an array of bits) * bit2pic.m (function: reverse of pic2bit) * encoder.(mexw***/mexa***/mexmaci***) (LDPC encoder binary files in Windows, Unix, MAC OSX) * decoder.(mexw***/mexa***/mexmaci***) (LDPC decoder binary files) * testcase * test.avi (testing video) * result * ldpcsnr3.jpg (example screenshot) ## show_pic_ber.m The main file contains the _gui_load_video_ function, which is the main processing block, It is executed everytime the __start-Butten__ was hit. It first get the data from a frame, pack it into a encoder blocks. On each blok, encode, modulation, mapping (demodulation), and decoding. Once all blocks of a frame is done, paint the result on GUI. And if __updating_new_frames__ option is selected, it will continue to the next frame. Otherwise, the program will stop.

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