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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=.
2prefix=/opt/rcq
3exec_prefix=${prefix}
4bindir=${exec_prefix}/bin
5libdir=${exec_prefix}/lib
6includedir=${prefix}/include
7ARCH=ARM
8SYS=LINUX
9CC=arm-xilinx-linux-gnueabi-gcc
10CFLAGS=-Wshadow -O3 -fno-fast-math -Wall -I. -I$(SRCPATH) -std=gnu99 -fPIC -fomit-frame-pointer -fno-tree-vectorize
11DEPMM=-MM -g0
12DEPMT=-MT
13LD=arm-xilinx-linux-gnueabi-gcc-o
14LDFLAGS= -lm -lpthread
15LIBX264=libx264.a
16AR=arm-xilinx-linux-gnueabi-arrc
17RANLIB=arm-xilinx-linux-gnueabi-ranlib
18STRIP=arm-xilinx-linux-gnueabi-strip
19AS=
20ASFLAGS= -DHAVE_ALIGNED_STACK=1-DPIC -DHIGH_BIT_DEPTH=0-DBIT_DEPTH=8
21RC=
22RCFLAGS=
23EXE=
24HAVE_GETOPT_LONG=1
25DEVNULL=/dev/null
26PROF_GEN_CC=-fprofile-generate
27PROF_GEN_LD=-fprofile-generate
28PROF_USE_CC=-fprofile-use
29PROF_USE_LD=-fprofile-use
30default: cli
31install: install-cli
32SOSUFFIX=so
33SONAME=libx264.so.129
34SOFLAGS=-shared -Wl,-soname,$(SONAME) -Wl,-Bsymbolic
35default: lib-shared
36install: install-lib-shared
37LDFLAGSCLI =
38CLI_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-mode0--b-adapt0--bframes0--no-cabac --no-deblock --no-mbtree --me dia --no-mixed-refs --partitions none --rc-lookahead0--ref1--scenecut0--subme0--trellis0

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 ( inwhich caseresolution 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

Two- pass with a bitrate of 1000kbps:
x264--pass 1--bitrate 1000-o

x264--pass 2--bitrate 1000-o

Lossless:
x264--qp 0-o

Maximum PSNR at the cost of speed and visual quality:
x264--preset placebo --tune psnr -o

Constant bitrate at 1000kbps with a 2second- buffer:
x264--vbv-bufsize 2000--bitrate 1000-o

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 forbit depth 8- 10 .
- high422:
No lossless.
Support forbit depth 8- 10 .
Support for 4: 2: 0/ 4: 2: 2 chroma subsampling.
- high444:
Support forbit 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 : 0.15
- animation (psy tuning):
--bframes {+ 2} --deblock 1: 1
--psy-rd 0.4: --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 : 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 " infinite "> Maximum GOP size [ 250 ]
-i, --min-keyint Minimum GOP size [auto]
--no-scenecut Disable adaptive I- frame decision
--scenecut How aggressively to insert extra I-frames [ 40 ]
--intra- refresh Use Periodic Intra Refresh instead of IDR frames
-b, --bframes Number of B-frames between I and P [ 3 ]
--b-adapt Adaptive B-frame decision method [ 1 ]
Higher values may lower threading efficiency.
- 0 : Disabled
- 1 : Fast
- 2: Optimal (slow with high -- bframes)
--b-bias 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 Number of reference frames [ 3 ]
--no- deblock Disable loop filter
-f, --deblock Loop filter parameters [ 0: 0 ]
--slices Number of slices per frame; forces rectangular
slices and is overridden by other slicing options
--slice-max-size Limit the size of each slice in bytes
--slice-max-mbs 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 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 Force constant QP ( 0- 69, 0= lossless)
-B, --bitrate Set bitrate (kbit/ s)
--crf < float> Quality-based VBR ( 0- 51) [ 23.0 ]
--rc-lookahead Number of frames forframetype lookahead [ 40 ]
--vbv-maxrate Max local bitrate (kbit/s) [ 0 ]
--vbv-bufsize 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 Set min QP [ 0 ]
--qpmax Set max QP [ 69 ]
--qpstep 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 QP difference between chroma and luma [ 0 ]
--aq-mode 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 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 2pass stats [ " x264_2pass.log " ]
--no-mbtree Disable mb- tree ratecontrol.
--qcomp < float> QP curve compression [ 0.60 ]
--cplxblur < float> Reduce fluctuations inQP (before curve compression) [ 20.0 ]
--qblur < float> Reduce fluctuations inQP (after curve compression) [ 0.5 ]
--zones // ... Tweak the bitrate of regions of the video
Each zone is of the form
,,
where is either
q= (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= 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 forB- frames
--weightp Weighted prediction forP-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 Maximum motion vector search range [ 16 ]
--mvrange Maximum motion vector length [- 1 (auto)]
--mvrange-thread < int> Minimum buffer between threads [- 1 (auto)]
-m, --subme 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 forI/P- frames
- 7: RD mode decision for all frames
- 8: RD refinement forI/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 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 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 inthe range 0- 32 .
--cqm < string> Preset quant matrices [ " flat " ]
- jvt, flat
--cqmfile < string> Read custom quant matrices froma JM- compatible file
Overrides any other--cqm* options.
--cqm4 Set all 4x4 quant matrices
Takes a comma-separated list of 16 integers.
--cqm8 Set all 8x8 quant matrices
Takes a comma-separated list of 64 integers.
--cqm4i, --cqm4p, --cqm8i, --cqm8p
Set both luma and chroma quant matrices
--cqm4iy, --cqm4ic, --cqm4py, --cqm4pc
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 Specify chroma sample location ( 0to 5) [ 0 ]
--nal-hrd < string> Signal HRD information (requires vbv- bufsize)
- none, vbr, cbr (cbr not allowed in .mp4)
--pic- structForce 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 Specify input bit depth for raw input
--input-range < string> Specify input color range [ " auto " ]
- auto, tv, pc
--input-res 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 First frame to encode
--frames Maximum number of frames to encode
--level < string> Specify level ( as defined by Annex A)
--bluray-compat Enable compatibility hacks forBlu- 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 Force a specific number of threads
--lookahead-threads 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 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,
asopposed to letting them select different algorithms
--asm 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 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
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 // ... Apply video filtering to the input file

Filter options may be specified in:= 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---> YUV4:2:0Y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---> YUV4:2:2Y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。