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Carte de Schillerkiez
13 mai 2011, par
Mis à jour : Septembre 2011
Langue : English
Type : Texte
Autres articles (111)
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Script d’installation automatique de MediaSPIP
25 avril 2011, parAfin de palier aux difficultés d’installation dues principalement aux dépendances logicielles coté serveur, un script d’installation "tout en un" en bash a été créé afin de faciliter cette étape sur un serveur doté d’une distribution Linux compatible.
Vous devez bénéficier d’un accès SSH à votre serveur et d’un compte "root" afin de l’utiliser, ce qui permettra d’installer les dépendances. Contactez votre hébergeur si vous ne disposez pas de cela.
La documentation de l’utilisation du script d’installation (...) -
Que fait exactement ce script ?
18 janvier 2011, parCe script est écrit en bash. Il est donc facilement utilisable sur n’importe quel serveur.
Il n’est compatible qu’avec une liste de distributions précises (voir Liste des distributions compatibles).
Installation de dépendances de MediaSPIP
Son rôle principal est d’installer l’ensemble des dépendances logicielles nécessaires coté serveur à savoir :
Les outils de base pour pouvoir installer le reste des dépendances Les outils de développements : build-essential (via APT depuis les dépôts officiels) ; (...) -
Automated installation script of MediaSPIP
25 avril 2011, parTo overcome the difficulties mainly due to the installation of server side software dependencies, an "all-in-one" installation script written in bash was created to facilitate this step on a server with a compatible Linux distribution.
You must have access to your server via SSH and a root account to use it, which will install the dependencies. Contact your provider if you do not have that.
The documentation of the use of this installation script is available here.
The code of this (...)
Sur d’autres sites (7056)
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Encoding/Decoding H264 using libav in C++ [closed]
20 mai, par gbock93I want to build an application to


- 

- capture frames in YUYV 4:2:2 format
- encode them to H264
- send over network
- decode the received data
- display the video stream












To do so I wrote 2 classes, H264Encoder and H264Decoder.


I post only the .cpp contents, the .h are trivial :


H264Encoder.cpp


#include 

#include <stdexcept>
#include <iostream>

H264Encoder::H264Encoder(unsigned int width_, unsigned int height_, unsigned int fps_):
 m_width(width_),
 m_height(height_),
 m_fps(fps_),
 m_frame_index(0),
 m_context(nullptr),
 m_frame(nullptr),
 m_packet(nullptr),
 m_sws_ctx(nullptr)
{
 // Find the video codec
 AVCodec* codec;
 codec = avcodec_find_encoder(AV_CODEC_ID_H264);
 if (!codec)
 throw std::runtime_error("[Encoder]: Error: Codec not found");

 // Allocate codec
 m_context = avcodec_alloc_context3(codec);
 if (!m_context)
 throw std::runtime_error("[Encoder]: Error: Could not allocate codec context");

 // Configure codec
 av_opt_set(m_context->priv_data, "preset", "ultrafast", 0);
 av_opt_set(m_context->priv_data, "tune", "zerolatency", 0);
 av_opt_set(m_context->priv_data, "crf", "35", 0); // Range: [0; 51], sane range: [18; 26], lower -> higher compression

 m_context->width = (int)width_;
 m_context->height = (int)height_;
 m_context->time_base = {1, (int)fps_};
 m_context->framerate = {(int)fps_, 1};
 m_context->codec_id = AV_CODEC_ID_H264;
 m_context->pix_fmt = AV_PIX_FMT_YUV420P; // H265|4 codec take as input only AV_PIX_FMT_YUV420P
 m_context->bit_rate = 400000;
 m_context->gop_size = 10;
 m_context->max_b_frames = 1;

 // Open codec
 if (avcodec_open2(m_context, codec, nullptr) < 0)
 throw std::runtime_error("[Encoder]: Error: Could not open codec");

 // Allocate frame and its buffer
 m_frame = av_frame_alloc();
 if (!m_frame) 
 throw std::runtime_error("[Encoder]: Error: Could not allocate frame");

 m_frame->format = m_context->pix_fmt;
 m_frame->width = m_context->width;
 m_frame->height = m_context->height;

 if (av_frame_get_buffer(m_frame, 0) < 0)
 throw std::runtime_error("[Encoder]: Error: Cannot allocate frame buffer");
 
 // Allocate packet
 m_packet = av_packet_alloc();
 if (!m_packet) 
 throw std::runtime_error("[Encoder]: Error: Could not allocate packet");

 // Convert from YUYV422 to YUV420P
 m_sws_ctx = sws_getContext(
 width_, height_, AV_PIX_FMT_YUYV422,
 width_, height_, AV_PIX_FMT_YUV420P,
 SWS_BILINEAR, nullptr, nullptr, nullptr
 );
 if (!m_sws_ctx) 
 throw std::runtime_error("[Encoder]: Error: Could not allocate sws context");

 //
 printf("[Encoder]: H264Encoder ready.\n");
}

H264Encoder::~H264Encoder()
{
 sws_freeContext(m_sws_ctx);
 av_packet_free(&m_packet);
 av_frame_free(&m_frame);
 avcodec_free_context(&m_context);

 printf("[Encoder]: H264Encoder destroyed.\n");
}

std::vector H264Encoder::encode(const cv::Mat& img_)
{
 /*
 - YUYV422 is a packed format. It has 3 components (av_pix_fmt_desc_get((AVPixelFormat)AV_PIX_FMT_YUYV422)->nb_components == 3) but
 data is stored in a single plane (av_pix_fmt_count_planes((AVPixelFormat)AV_PIX_FMT_YUYV422) == 1).
 - YUV420P is a planar format. It has 3 components (av_pix_fmt_desc_get((AVPixelFormat)AV_PIX_FMT_YUV420P)->nb_components == 3) and
 each component is stored in a separate plane (av_pix_fmt_count_planes((AVPixelFormat)AV_PIX_FMT_YUV420P) == 3) with its
 own stride.
 */
 std::cout << "[Encoder]" << std::endl;
 std::cout << "[Encoder]: Encoding img " << img_.cols << "x" << img_.rows << " | element size " << img_.elemSize() << std::endl;
 assert(img_.elemSize() == 2);

 uint8_t* input_data[1] = {(uint8_t*)img_.data};
 int input_linesize[1] = {2 * (int)m_width};
 
 if (av_frame_make_writable(m_frame) < 0)
 throw std::runtime_error("[Encoder]: Error: Cannot make frame data writable");

 // Convert from YUV422 image to YUV420 frame. Apply scaling if necessary
 sws_scale(
 m_sws_ctx,
 input_data, input_linesize, 0, m_height,
 m_frame->data, m_frame->linesize
 );
 m_frame->pts = m_frame_index;

 int n_planes = av_pix_fmt_count_planes((AVPixelFormat)m_frame->format);
 std::cout << "[Encoder]: Sending Frame " << m_frame_index << " with dimensions " << m_frame->width << "x" << m_frame->height << "x" << n_planes << std::endl;
 for (int i=0; iframerate.num) + 1;
 break;
 case AVERROR(EAGAIN):
 throw std::runtime_error("[Encoder]: avcodec_send_frame: EAGAIN");
 case AVERROR_EOF:
 throw std::runtime_error("[Encoder]: avcodec_send_frame: EOF");
 case AVERROR(EINVAL):
 throw std::runtime_error("[Encoder]: avcodec_send_frame: EINVAL");
 case AVERROR(ENOMEM):
 throw std::runtime_error("[Encoder]: avcodec_send_frame: ENOMEM");
 default:
 throw std::runtime_error("[Encoder]: avcodec_send_frame: UNKNOWN");
 }

 // Receive packet from codec
 std::vector result;
 while(ret >= 0)
 {
 ret = avcodec_receive_packet(m_context, m_packet);

 switch (ret)
 {
 case 0:
 std::cout << "[Encoder]: Received packet from codec of size " << m_packet->size << " bytes " << std::endl;
 result.insert(result.end(), m_packet->data, m_packet->data + m_packet->size);
 av_packet_unref(m_packet);
 break;

 case AVERROR(EAGAIN):
 std::cout << "[Encoder]: avcodec_receive_packet: EAGAIN" << std::endl;
 break;
 case AVERROR_EOF:
 std::cout << "[Encoder]: avcodec_receive_packet: EOF" << std::endl;
 break;
 case AVERROR(EINVAL):
 throw std::runtime_error("[Encoder]: avcodec_receive_packet: EINVAL");
 default:
 throw std::runtime_error("[Encoder]: avcodec_receive_packet: UNKNOWN");
 }
 }

 std::cout << "[Encoder]: Encoding complete" << std::endl;
 return result;
}
</iostream></stdexcept>

H264Decoder.cpp


#include 

#include <iostream>
#include <stdexcept>

H264Decoder::H264Decoder():
 m_context(nullptr),
 m_frame(nullptr),
 m_packet(nullptr)
{
 // Find the video codec
 AVCodec* codec;
 codec = avcodec_find_decoder(AV_CODEC_ID_H264);
 if (!codec)
 throw std::runtime_error("[Decoder]: Error: Codec not found");

 // Allocate codec
 m_context = avcodec_alloc_context3(codec);
 if (!m_context)
 throw std::runtime_error("[Decoder]: Error: Could not allocate codec context");

 // Open codec
 if (avcodec_open2(m_context, codec, nullptr) < 0)
 throw std::runtime_error("[Decoder]: Error: Could not open codec");

 // Allocate frame
 m_frame = av_frame_alloc();
 if (!m_frame)
 throw std::runtime_error("[Decoder]: Error: Could not allocate frame");

 // Allocate packet
 m_packet = av_packet_alloc();
 if (!m_packet) 
 throw std::runtime_error("[Decoder]: Error: Could not allocate packet");

 //
 printf("[Decoder]: H264Decoder ready.\n");
}

H264Decoder::~H264Decoder()
{
 av_packet_free(&m_packet);
 av_frame_free(&m_frame);
 avcodec_free_context(&m_context);

 printf("[Decoder]: H264Decoder destroyed.\n");
}

bool H264Decoder::decode(uint8_t* data_, size_t size_, cv::Mat& img_)
{
 std::cout << "[Decoder]" << std::endl;
 std::cout << "[Decoder]: decoding " << size_ << " bytes of data" << std::endl;

 // Fill packet
 m_packet->data = data_;
 m_packet->size = size_;

 if (size_ == 0)
 return false;

 // Send packet to codec
 int send_result = avcodec_send_packet(m_context, m_packet);

 switch (send_result)
 {
 case 0:
 std::cout << "[Decoder]: Sent packet to codec" << std::endl;
 break;
 case AVERROR(EAGAIN):
 throw std::runtime_error("[Decoder]: avcodec_send_packet: EAGAIN");
 case AVERROR_EOF:
 throw std::runtime_error("[Decoder]: avcodec_send_packet: EOF");
 case AVERROR(EINVAL):
 throw std::runtime_error("[Decoder]: avcodec_send_packet: EINVAL");
 case AVERROR(ENOMEM):
 throw std::runtime_error("[Decoder]: avcodec_send_packet: ENOMEM");
 default:
 throw std::runtime_error("[Decoder]: avcodec_send_packet: UNKNOWN");
 }

 // Receive frame from codec
 int n_planes;
 uint8_t* output_data[1];
 int output_line_size[1];

 int receive_result = avcodec_receive_frame(m_context, m_frame);

 switch (receive_result)
 {
 case 0:
 n_planes = av_pix_fmt_count_planes((AVPixelFormat)m_frame->format);
 std::cout << "[Decoder]: Received Frame with dimensions " << m_frame->width << "x" << m_frame->height << "x" << n_planes << std::endl;
 for (int i=0; i/
 std::cout << "[Decoder]: Decoding complete" << std::endl;
 return true;
}
</stdexcept></iostream>

To test the two classes I put together a main.cpp to grab a frame, encode/decode and display the decoded frame (no network transmission in place) :


main.cpp


while(...)
{
 // get frame from custom camera class. Format is YUYV 4:2:2
 camera.getFrame(camera_frame);
 // Construct a cv::Mat to represent the grabbed frame
 cv::Mat camera_frame_yuyv = cv::Mat(camera_frame.height, camera_frame.width, CV_8UC2, camera_frame.data.data());
 // Encode image
 std::vector encoded_data = encoder.encode(camera_frame_yuyv);
 if (!encoded_data.empty())
 {
 // Decode image
 cv::Mat decoded_frame;
 if (decoder.decode(encoded_data.data(), encoded_data.size(), decoded_frame))
 {
 // Display image
 cv::imshow("Camera", decoded_frame);
 cv::waitKey(1);
 }
 }
}


Compiling and executing the code I get random results between subsequent executions :


- 

- Sometimes the whole loop runs without problems and I see the decoded image.
- Sometimes the program crashes at the
sws_scale(...)call in the decoder with"Assertion desc failed at src/libswscale/swscale_internal.h:757". - Sometimes the loop runs but I see a black image and the message
Slice parameters 0, 720 are invalidis displayed when executing thesws_scale(...)call in the decoder.








Why is the behaviour so random ? What am I doing wrong with the libav API ?


Some resources I found useful :


- 

- This article on encoding
- This article on decoding






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FFMpeg for IOS - Disabling Log Levels
12 novembre 2013, par VeeruI have compiled ffmpeg for ios. The configuration for compiling, i have borrowed from kxmovie's Rake file.
Everything works fine, but i would like to disable all the debug messages showed in console by the decoder.
How can i achieve this. I believe it should be the ffmpeg is compiled, but am not sure how to go about it. Any suggestions would be highly appreciated.
configure command :
./configure —disable-ffmpeg —disable-ffplay —disable-ffserver
—disable-ffprobe —disable-doc —disable-bzlib —target-os=darwin —enable-cross-compile —enable-gpl —enable-version3 —assert-level=2 —disable-mmx —arch=i386 —cpu=i386 —extra-ldflags='-arch i386' —extra-cflags='-arch i386' —disable-asm —cc=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc
—as='gas-preprocessor.pl /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin/gcc'
—sysroot=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk
—extra-ldflags=-L/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator6.1.sdk/usr/lib/system -
FFMPEG compile on OS X 10.9 Mavericks with deployment target 10.6
14 novembre 2013, par Infinite PossibilitiesI am trying to build ffmepg on OS X 10.9 and everything works correctly, but it seems that the deployment target is ignored. Here is how I am configuring the ffmpeg :
export LDFLAGS="-L${TARGET}/lib $CFLAGS"
export CFLAGS="-I${TARGET}/include $LDFLAGS -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.6.sdk -mmacosx-version-min=10.6"
./configure --prefix=${TARGET}/compile --cc=clang --as=yasm --extra-version=inpos --disable-shared --enable-static --disable-ffplay --disable-ffserver --enable-gpl --enable-pthreads --enable-postproc --enable-gray --enable-libfaac --enable-libmp3lame --enable-libtheora --enable-libxvid --enable-libspeex --enable-bzlib --enable-zlib --enable-nonfree --enable-version3 --enable-libgsm --enable-libopencore-amrnb --enable-libopencore-amrwbIs there any problem that causes the
mmacosx-version-min=10.6to be ignored ?
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