在(原创)基于ZedBoard的Webcam设计(四):MJPG编码和AVI封装中，我们在zed上完成了视频的采集和存储，但是MJPG只是对一帧一帧图片进行编码，编码效率只有10%。x264-snapshot提供了开源x264源代码，已经广泛用于嵌入式解决方案中。本小节将介绍zed上x264-snapshot源码的配置，并在zed上使用High版本、main版本对一个33M的测试视频进行编码，测试编码效率。
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相关阅读：
(原创)基于ZedBoard的Webcam设计(一)：USB摄像头(V4L2接口)的图片采集
(原创)基于ZedBoard的Webcam设计(二)：USB摄像头图片采集+QT显示
(原创)基于ZedBoard的Webcam设计(三)：视频的采集和动态显示
(原创)基于ZedBoard的Webcam设计(四)：MJPG编码和AVI封装
(原创)基于ZedBoard的Webcam设计(五)：x264编码在zedboard上的实现(软编码)
硬件平台：Digilent ZedBoard
开发环境：Windows XP 32 bit + Wmare 8.0 + Ubuntu 10.04 +Qt+ arm-linux-xilinx-gnueabi交叉编译环境
Zedboard linux: Digilent OOB Design
一、x264开源包获取
x264-snapshot提供了开源x264源代码，已经在X86和ARM架构下均已实现。linux下可以使用git获得最新的代码包
git clone git://git.videolan.org/x264.git
也可以通过网页下载：
http://download.videolan.org/pub/videolan/x264/snapshots/
二、配置、安装x264-snapshot
下载到源码后，对其进行配置，以便在后续make时编译出zed上可以运行的可执行程序
1、解压源码包后，进入源码目录
./configure --host=arm-xilinx-linux-gnueabi --prefix=/opt/rcq --enable-shared --disable-asm
congfig之后，设定了host为arm-xilinx-linux-gnueabi，install路径是/opt/rcq
2、修改config.mak文件
针对zed的gcc，需要修改config.mak文件
1 SRCPATH=. 2 prefix=/opt/rcq 3 exec_prefix=${prefix} 4 bindir=${exec_prefix}/bin 5 libdir=${exec_prefix}/lib 6 includedir=${prefix}/include 7 ARCH=ARM 8 SYS=LINUX 9 CC=arm-xilinx-linux-gnueabi-gcc 10 CFLAGS=-Wshadow -O3 -fno-fast-math -Wall -I. -I$(SRCPATH) -std=gnu99 -fPIC -fomit-frame-pointer -fno-tree-vectorize 11 DEPMM=-MM -g0 12 DEPMT=-MT 13 LD=arm-xilinx-linux-gnueabi-gcc -o 14 LDFLAGS= -lm -lpthread 15 LIBX264=libx264.a 16 AR=arm-xilinx-linux-gnueabi-ar rc 17 RANLIB=arm-xilinx-linux-gnueabi-ranlib 18 STRIP=arm-xilinx-linux-gnueabi-strip 19 AS= 20 ASFLAGS= -DHAVE_ALIGNED_STACK=1 -DPIC -DHIGH_BIT_DEPTH=0 -DBIT_DEPTH=8 21 RC= 22 RCFLAGS= 23 EXE= 24 HAVE_GETOPT_LONG=1 25 DEVNULL=/dev/null 26 PROF_GEN_CC=-fprofile-generate 27 PROF_GEN_LD=-fprofile-generate 28 PROF_USE_CC=-fprofile-use 29 PROF_USE_LD=-fprofile-use 30 default: cli 31 install: install-cli 32 SOSUFFIX=so 33 SONAME=libx264.so.129 34 SOFLAGS=-shared -Wl,-soname,$(SONAME) -Wl,-Bsymbolic 35 default: lib-shared 36 install: install-lib-shared 37 LDFLAGSCLI = 38 CLI_LIBX264 = $(LIBX264)
其中9、13、16、17、18行为修改后的。
3、make
make install
make
完运行库的安装和成执行文件的生成
三、在zed上测试x264
将可执行x264和测试rcq.yuv文件拷贝到zed上，使用默认运行命令
./x264 rcq.yuv --input-res 640x480 -o rcq.flv
其中--input-res 640x480设定输入yuv视频帧的大小，rcq.flv是输出文件，可以设定为.mkv/.mp4/H264等。从控制台可以看到
使用的profile是最高等级High level 3.0，但是的编码速率只有1.40fps……情何以堪……
编码结束后：
生成的rcq.flv文件大小348k，相比较原来的rcq.yuv文件大小33M，压缩率在1%。
可以使用最快编码方式，命令和参数如下
./x264 rcq.yuv --input-res 640x480 -o rcq.flv --no-8x8dct --aq-mode 0 --b-adapt 0 --bframes 0 --no-cabac --no-deblock --no-mbtree --me dia --no-mixed-refs --partitions none --rc-lookahead 0 --ref 1 --scenecut 0 --subme 0 --trellis 0
编码速率能有22fps，这样还凑合。生成的rcq.flv文件大小787K，压缩率在5%。
四、x264命令和参数(fullhelp)
View Code
Syntax: x264 [options] -o outfile infile Infile can be raw (in which case resolution is required), or YUV4MPEG (*.y4m), or Avisynth if compiled with support (no). or libav* formats if compiled with lavf support (no) or ffms support (no). Outfile type is selected by filename: .264 -> Raw bytestream .mkv -> Matroska .flv -> Flash Video .mp4 -> MP4 if compiled with GPAC support (no) Output bit depth: 8 (configured at compile time) Options: -h, --help List basic options --longhelp List more options --fullhelp List all options Example usage: Constant quality mode: x264 --crf 24 -o <output> <input> Two-pass with a bitrate of 1000kbps: x264 --pass 1 --bitrate 1000 -o <output> <input> x264 --pass 2 --bitrate 1000 -o <output> <input> Lossless: x264 --qp 0 -o <output> <input> Maximum PSNR at the cost of speed and visual quality: x264 --preset placebo --tune psnr -o <output> <input> Constant bitrate at 1000kbps with a 2 second-buffer: x264 --vbv-bufsize 2000 --bitrate 1000 -o <output> <input> Presets: --profile <string> Force the limits of an H.264 profile Overrides all settings. - baseline: --no-8x8dct --bframes 0 --no-cabac --cqm flat --weightp 0 No interlaced. No lossless. - main: --no-8x8dct --cqm flat No lossless. - high: No lossless. - high10: No lossless. Support for bit depth 8-10. - high422: No lossless. Support for bit depth 8-10. Support for 4:2:0/4:2:2 chroma subsampling. - high444: Support for bit depth 8-10. Support for 4:2:0/4:2:2/4:4:4 chroma subsampling. --preset <string> Use a preset to select encoding settings [medium] Overridden by user settings. - ultrafast: --no-8x8dct --aq-mode 0 --b-adapt 0 --bframes 0 --no-cabac --no-deblock --no-mbtree --me dia --no-mixed-refs --partitions none --rc-lookahead 0 --ref 1 --scenecut 0 --subme 0 --trellis 0 --no-weightb --weightp 0 - superfast: --no-mbtree --me dia --no-mixed-refs --partitions i8x8,i4x4 --rc-lookahead 0 --ref 1 --subme 1 --trellis 0 --weightp 1 - veryfast: --no-mixed-refs --rc-lookahead 10 --ref 1 --subme 2 --trellis 0 --weightp 1 - faster: --no-mixed-refs --rc-lookahead 20 --ref 2 --subme 4 --weightp 1 - fast: --rc-lookahead 30 --ref 2 --subme 6 --weightp 1 - medium: Default settings apply. - slow: --b-adapt 2 --direct auto --me umh --rc-lookahead 50 --ref 5 --subme 8 - slower: --b-adapt 2 --direct auto --me umh --partitions all --rc-lookahead 60 --ref 8 --subme 9 --trellis 2 - veryslow: --b-adapt 2 --bframes 8 --direct auto --me umh --merange 24 --partitions all --ref 16 --subme 10 --trellis 2 --rc-lookahead 60 - placebo: --bframes 16 --b-adapt 2 --direct auto --slow-firstpass --no-fast-pskip --me tesa --merange 24 --partitions all --rc-lookahead 60 --ref 16 --subme 11 --trellis 2 --tune <string> Tune the settings for a particular type of source or situation Overridden by user settings. Multiple tunings are separated by commas. Only one psy tuning can be used at a time. - film (psy tuning): --deblock -1:-1 --psy-rd <unset>:0.15 - animation (psy tuning): --bframes {+2} --deblock 1:1 --psy-rd 0.4:<unset> --aq-strength 0.6 --ref {Double if >1 else 1} - grain (psy tuning): --aq-strength 0.5 --no-dct-decimate --deadzone-inter 6 --deadzone-intra 6 --deblock -2:-2 --ipratio 1.1 --pbratio 1.1 --psy-rd <unset>:0.25 --qcomp 0.8 - stillimage (psy tuning): --aq-strength 1.2 --deblock -3:-3 --psy-rd 2.0:0.7 - psnr (psy tuning): --aq-mode 0 --no-psy - ssim (psy tuning): --aq-mode 2 --no-psy \ - fastdecode: --no-cabac --no-deblock --no-weightb --weightp 0 - zerolatency: --bframes 0 --force-cfr --no-mbtree --sync-lookahead 0 --sliced-threads --rc-lookahead 0 --slow-firstpass Don't force these faster settings with --pass 1: --no-8x8dct --me dia --partitions none --ref 1 --subme {2 if >2 else unchanged} --trellis 0 --fast-pskip Frame-type options: -I, --keyint <integer or "infinite"> Maximum GOP size [250] -i, --min-keyint <integer> Minimum GOP size [auto] --no-scenecut Disable adaptive I-frame decision --scenecut <integer> How aggressively to insert extra I-frames [40] --intra-refresh Use Periodic Intra Refresh instead of IDR frames -b, --bframes <integer> Number of B-frames between I and P [3] --b-adapt <integer> Adaptive B-frame decision method [1] Higher values may lower threading efficiency. - 0: Disabled - 1: Fast - 2: Optimal (slow with high --bframes) --b-bias <integer> Influences how often B-frames are used [0] --b-pyramid <string> Keep some B-frames as references [normal] - none: Disabled - strict: Strictly hierarchical pyramid - normal: Non-strict (not Blu-ray compatible) --open-gop Use recovery points to close GOPs Only available with b-frames --no-cabac Disable CABAC -r, --ref <integer> Number of reference frames [3] --no-deblock Disable loop filter -f, --deblock <alpha:beta> Loop filter parameters [0:0] --slices <integer> Number of slices per frame; forces rectangular slices and is overridden by other slicing options --slice-max-size <integer> Limit the size of each slice in bytes --slice-max-mbs <integer> Limit the size of each slice in macroblocks --tff Enable interlaced mode (top field first) --bff Enable interlaced mode (bottom field first) --constrained-intra Enable constrained intra prediction. --pulldown <string> Use soft pulldown to change frame rate - none, 22, 32, 64, double, triple, euro (requires cfr input) --fake-interlaced Flag stream as interlaced but encode progressive. Makes it possible to encode 25p and 30p Blu-Ray streams. Ignored in interlaced mode. --frame-packing <integer> For stereoscopic videos define frame arrangement - 0: checkerboard - pixels are alternatively from L and R - 1: column alternation - L and R are interlaced by column - 2: row alternation - L and R are interlaced by row - 3: side by side - L is on the left, R on the right - 4: top bottom - L is on top, R on bottom - 5: frame alternation - one view per frame Ratecontrol: -q, --qp <integer> Force constant QP (0-69, 0=lossless) -B, --bitrate <integer> Set bitrate (kbit/s) --crf <float> Quality-based VBR (0-51) [23.0] --rc-lookahead <integer> Number of frames for frametype lookahead [40] --vbv-maxrate <integer> Max local bitrate (kbit/s) [0] --vbv-bufsize <integer> Set size of the VBV buffer (kbit) [0] --vbv-init <float> Initial VBV buffer occupancy [0.9] --crf-max <float> With CRF+VBV, limit RF to this value May cause VBV underflows! --qpmin <integer> Set min QP [0] --qpmax <integer> Set max QP [69] --qpstep <integer> Set max QP step [4] --ratetol <float> Tolerance of ABR ratecontrol and VBV [1.0] --ipratio <float> QP factor between I and P [1.40] --pbratio <float> QP factor between P and B [1.30] --chroma-qp-offset <integer> QP difference between chroma and luma [0] --aq-mode <integer> AQ method [1] - 0: Disabled - 1: Variance AQ (complexity mask) - 2: Auto-variance AQ (experimental) --aq-strength <float> Reduces blocking and blurring in flat and textured areas. [1.0] -p, --pass <integer> Enable multipass ratecontrol - 1: First pass, creates stats file - 2: Last pass, does not overwrite stats file - 3: Nth pass, overwrites stats file --stats <string> Filename for 2 pass stats ["x264_2pass.log"] --no-mbtree Disable mb-tree ratecontrol. --qcomp <float> QP curve compression [0.60] --cplxblur <float> Reduce fluctuations in QP (before curve compression) [20.0] --qblur <float> Reduce fluctuations in QP (after curve compression) [0.5] --zones <zone0>/<zone1>/... Tweak the bitrate of regions of the video Each zone is of the form <start frame>,<end frame>,<option> where <option> is either q=<integer> (force QP) or b=<float> (bitrate multiplier) --qpfile <string> Force frametypes and QPs for some or all frames Format of each line: framenumber frametype QP QP is optional (none lets x264 choose). Frametypes: I,i,K,P,B,b. K=<I or i> depending on open-gop setting QPs are restricted by qpmin/qpmax. Analysis: -A, --partitions <string> Partitions to consider ["p8x8,b8x8,i8x8,i4x4"] - p8x8, p4x4, b8x8, i8x8, i4x4 - none, all (p4x4 requires p8x8. i8x8 requires --8x8dct.) --direct <string> Direct MV prediction mode ["spatial"] - none, spatial, temporal, auto --no-weightb Disable weighted prediction for B-frames --weightp <integer> Weighted prediction for P-frames [2] - 0: Disabled - 1: Weighted refs - 2: Weighted refs + Duplicates --me <string> Integer pixel motion estimation method ["hex"] - dia: diamond search, radius 1 (fast) - hex: hexagonal search, radius 2 - umh: uneven multi-hexagon search - esa: exhaustive search - tesa: hadamard exhaustive search (slow) --merange <integer> Maximum motion vector search range [16] --mvrange <integer> Maximum motion vector length [-1 (auto)] --mvrange-thread <int> Minimum buffer between threads [-1 (auto)] -m, --subme <integer> Subpixel motion estimation and mode decision [7] - 0: fullpel only (not recommended) - 1: SAD mode decision, one qpel iteration - 2: SATD mode decision - 3-5: Progressively more qpel - 6: RD mode decision for I/P-frames - 7: RD mode decision for all frames - 8: RD refinement for I/P-frames - 9: RD refinement for all frames - 10: QP-RD - requires trellis=2, aq-mode>0 - 11: Full RD: disable all early terminations --psy-rd <float:float> Strength of psychovisual optimization ["1.0:0.0"] #1: RD (requires subme>=6) #2: Trellis (requires trellis, experimental) --no-psy Disable all visual optimizations that worsen both PSNR and SSIM. --no-mixed-refs Don't decide references on a per partition basis --no-chroma-me Ignore chroma in motion estimation --no-8x8dct Disable adaptive spatial transform size -t, --trellis <integer> Trellis RD quantization. [1] - 0: disabled - 1: enabled only on the final encode of a MB - 2: enabled on all mode decisions --no-fast-pskip Disables early SKIP detection on P-frames --no-dct-decimate Disables coefficient thresholding on P-frames --nr <integer> Noise reduction [0] --deadzone-inter <int> Set the size of the inter luma quantization deadzone [21] --deadzone-intra <int> Set the size of the intra luma quantization deadzone [11] Deadzones should be in the range 0 - 32. --cqm <string> Preset quant matrices ["flat"] - jvt, flat --cqmfile <string> Read custom quant matrices from a JM-compatible file Overrides any other --cqm* options. --cqm4 <list> Set all 4x4 quant matrices Takes a comma-separated list of 16 integers. --cqm8 <list> Set all 8x8 quant matrices Takes a comma-separated list of 64 integers. --cqm4i, --cqm4p, --cqm8i, --cqm8p <list> Set both luma and chroma quant matrices --cqm4iy, --cqm4ic, --cqm4py, --cqm4pc <list> Set individual quant matrices Video Usability Info (Annex E): The VUI settings are not used by the encoder but are merely suggestions to the playback equipment. See doc/vui.txt for details. Use at your own risk. --overscan <string> Specify crop overscan setting ["undef"] - undef, show, crop --videoformat <string> Specify video format ["undef"] - component, pal, ntsc, secam, mac, undef --range <string> Specify color range ["auto"] - auto, tv, pc --colorprim <string> Specify color primaries ["undef"] - undef, bt709, bt470m, bt470bg smpte170m, smpte240m, film --transfer <string> Specify transfer characteristics ["undef"] - undef, bt709, bt470m, bt470bg, linear, log100, log316, smpte170m, smpte240m --colormatrix <string> Specify color matrix setting ["???"] - undef, bt709, fcc, bt470bg smpte170m, smpte240m, GBR, YCgCo --chromaloc <integer> Specify chroma sample location (0 to 5) [0] --nal-hrd <string> Signal HRD information (requires vbv-bufsize) - none, vbr, cbr (cbr not allowed in .mp4) --pic-struct Force pic_struct in Picture Timing SEI --crop-rect <string> Add 'left,top,right,bottom' to the bitstream-level cropping rectangle Input/Output: -o, --output <string> Specify output file --muxer <string> Specify output container format ["auto"] - auto, raw, mkv, flv --demuxer <string> Specify input container format ["auto"] - auto, raw, y4m --input-fmt <string> Specify input file format (requires lavf support) --input-csp <string> Specify input colorspace format for raw input - valid csps for `raw' demuxer: i420, yv12, nv12, i422, yv16, nv16, i444, yv24, bgr, bgra, rgb --output-csp <string> Specify output colorspace ["i420"] - i420, i422, i444, rgb --input-depth <integer> Specify input bit depth for raw input --input-range <string> Specify input color range ["auto"] - auto, tv, pc --input-res <intxint> Specify input resolution (width x height) --index <string> Filename for input index file --sar height Specify Sample Aspect Ratio --fps <float|rational> Specify framerate --seek <integer> First frame to encode --frames <integer> Maximum number of frames to encode --level <string> Specify level (as defined by Annex A) --bluray-compat Enable compatibility hacks for Blu-ray support -v, --verbose Print stats for each frame --no-progress Don't show the progress indicator while encoding --quiet Quiet Mode --log-level <string> Specify the maximum level of logging ["info"] - none, error, warning, info, debug --psnr Enable PSNR computation --ssim Enable SSIM computation --threads <integer> Force a specific number of threads --lookahead-threads <integer> Force a specific number of lookahead threads --sliced-threads Low-latency but lower-efficiency threading --thread-input Run Avisynth in its own thread --sync-lookahead <integer> Number of buffer frames for threaded lookahead --non-deterministic Slightly improve quality of SMP, at the cost of repeatability --cpu-independent Ensure exact reproducibility across different cpus, as opposed to letting them select different algorithms --asm <integer> Override CPU detection --no-asm Disable all CPU optimizations --visualize Show MB types overlayed on the encoded video --dump-yuv <string> Save reconstructed frames --sps-id <integer> Set SPS and PPS id numbers [0] --aud Use access unit delimiters --force-cfr Force constant framerate timestamp generation --tcfile-in <string> Force timestamp generation with timecode file --tcfile-out <string> Output timecode v2 file from input timestamps --timebase <int/int> Specify timebase numerator and denominator <integer> Specify timebase numerator for input timecode file or specify timebase denominator for other input --dts-compress Eliminate initial delay with container DTS hack Filtering: --vf, --video-filter <filter0>/<filter1>/... Apply video filtering to the input file Filter options may be specified in <filter>:<option>=<value> format. Available filters: crop:left,top,right,bottom removes pixels from the edges of the frame select_every:step,offset1[,...] apply a selection pattern to input frames step: the number of frames in the pattern offsets: the offset into the step to select a frame see: http://avisynth.org/mediawiki/Select#SelectEvery
五、关于YUV420的格式说明
YUV格式有两大类：planar和packed。 对于planar的YUV格式，先连续存储所有像素点的Y，紧接着存储所有像素点的U，随后是所有像素点的V。 对于packed的YUV格式，每个像素点的Y,U,V是连续交*存储的。 一般的录像程序是先从摄像头得到yuv420 planar的数据，然后编码成h264格式 帧，最后存储成3gp/mpeg等格式的视频文件。 以720×488大小图象YUV420 planar为例，其存储格式是： 共大小为(720×480×3>>1)字节，分为三个部分:Y,U和V Y分量： (720×480)个字节 U(Cb)分量：(720×480>>2)个字节 V(Cr)分量：(720×480>>2)个字节 三个部分内部均是行优先存储，三个部分之间是Y,U,V 顺序存储。 即YUV数据的0－－720×480字节是Y分量值， 720×480－－720×480×5/4字节是U分量 720×480×5/4 －－720×480×3/2字节是V分量。 一副w*h的yuv420图像数据的大小为w*h*1.5。 4 ：2： 2 和4：2：0 转换： 最简单的方式： YUV4:2:2 ---> YUV4:2:0 Y不变，将U和V信号值在行(垂直方向)在进行一次隔行抽样。 YUV4:2:0 ---> YUV4:2:2 Y不变，将U和V信号值的每一行分别拷贝一份形成连续两行数据。
六、测试视频
=====================================================
0、x264-snapshots:http://download.videolan.org/pub/videolan/x264/snapshots/
1、zed可执行文件：x264.rar
2、测试yuv文件：rcq.part1.rar rcq.part2.rar
3、其他通用测试yuv序列：http://www.cipr.rpi.edu/resource/sequences/sif.html