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。
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)
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 width: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。
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