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Thread: Create video widget using byte array

  1. 13th June 2012, 19:15 #1
    Elv13
    Elv13 is offline Beginner
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    Default Create video widget using byte array

    Hi,

    I have access to a framebuffer using SHM on Linux. I can get access to the data and I am quite sure they are valid. However, it only work at small resolution and somehow I get overscroll video. I try to use QImage and tried many combinaisons. Most wont work above 160x120. This one work with 340x240, but not above. The CPU does not seem to be the problem, my app use little. I can't use OpenGL (not supported on device)..

    What is the best way to make a video from a frame buffer?

    This is the current code:
    Qt Code: 
    1. VideoWidget::VideoWidget(QWidget* parent) : QWidget(parent),m_Image(NULL) {
    2.    setMinimumSize(200,200);
    3.    connect(VideoModel::getInstance(),SIGNAL(frameUpdated()),this,SLOT(repaint2()));
    4. }
    5.  
    6. void VideoWidget::update() {
    7.    QPainter painter(this);
    8.    painter.drawImage(QRect(0,0,width(),height()),*(m_Image));
    9.    painter.end();
    10. }
    11.  
    12. void VideoWidget::paintEvent(QPaintEvent* event)
    13. {
    14.    Q_UNUSED(event)
    15.    if (VideoModel::getInstance()->isPreviewing()) {
    16.       update();
    17.    }
    18. }
    19.  
    20. void VideoWidget::repaint2()
    21. {
    22.    QSize size(VideoModel::getInstance()->getActiveResolution().width, VideoModel::getInstance()->getActiveResolution().height);
    23.    if (size != minimumSize())
    24.       setMinimumSize(size);
    25.    //if (m_Image)
    26.    //   delete m_Image;
    27.    m_Image = new QImage(size,QImage::Format_ARGB32);
    28.    m_Image->loadFromData(VideoModel::getInstance()->getCurrentFrame(),"BMP");
    29.    repaint();
    30. }
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    Qt Code: 
    1. /************************************************************************************
    2.  *   Copyright (C) 2012 by Savoir-Faire Linux                                       *
    3.  *   Author : Emmanuel Lepage Vallee <emmanuel.lepage@savoirfairelinux.com>         *
    4.  *                                                                                  *
    5.  *   This library is free software; you can redistribute it and/or                  *
    6.  *   modify it under the terms of the GNU Lesser General Public                     *
    7.  *   License as published by the Free Software Foundation; either                   *
    8.  *   version 2.1 of the License, or (at your option) any later version.             *
    9.  *                                                                                  *
    10.  *   This library is distributed in the hope that it will be useful,                *
    11.  *   but WITHOUT ANY WARRANTY; without even the implied warranty of                 *
    12.  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU              *
    13.  *   Lesser General Public License for more details.                                *
    14.  *                                                                                  *
    15.  *   You should have received a copy of the GNU Lesser General Public               *
    16.  *   License along with this library; if not, write to the Free Software            *
    17.  *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA *
    18.  ***********************************************************************************/
    19. #include "VideoModel.h"
    20. #include "video_interface_singleton.h"
    21. #include <QSharedMemory>
    22. #include <QDBusPendingReply>
    23. #include <sys/ipc.h>
    24. #include <sys/sem.h>
    25. #include <sys/shm.h>
    26. #include <unistd.h>
    27.  
    28. VideoModel* VideoModel::m_spInstance = NULL;
    29.  
    30. ///@namespace ShmManager Low level function to access shared memory
    31. namespace ShmManager {
    32.    static int getShm(unsigned numBytes, int shmKey)
    33.    {
    34.       key_t key = shmKey;
    35.       int shm_id = shmget(key, numBytes, 0644);
    36.  
    37.       if (shm_id == -1)
    38.          qDebug() << ("shmget");
    39.  
    40.       return shm_id;
    41.    }
    42.  
    43.  
    44.    static void * attachShm(int shm_id)
    45.    {
    46.       void *data = shmat(shm_id, (void *)0, 0);
    47.       if (data == (char *)(-1)) {
    48.          qDebug() << ("shmat");
    49.          data = NULL;
    50.       }
    51.  
    52.       return data;
    53.    }
    54.  
    55.  
    56.    static void detachShm(char *data)
    57.    {
    58.       /* detach from the segment: */
    59.       if (shmdt(data) == -1)
    60.          qDebug() << ("shmdt");
    61.    }
    62.  
    63.    #if _SEM_SEMUN_UNDEFINED
    64.    union semun
    65.    {
    66.       int                 val  ; /* value for SETVAL */
    67.       struct semid_ds*    buf  ; /* buffer for IPC_STAT & IPC_SET */
    68.       unsigned short int* array; /* array for GETALL & SETALL */
    69.       struct seminfo*     __buf; /* buffer for IPC_INFO */
    70.    };
    71.    #endif
    72.  
    73.    static int get_sem_set(int semKey)
    74.    {
    75.       int sem_set_id;
    76.       key_t key = semKey;
    77.  
    78.       union semun sem_val;
    79.  
    80.       sem_set_id = semget(key, 1, 0600);
    81.       if (sem_set_id == -1) {
    82.          qDebug() << ("semget");
    83.          return sem_set_id;
    84.       }
    85.       sem_val.val = 0;
    86.       semctl(sem_set_id, 0, SETVAL, sem_val);
    87.       return sem_set_id;
    88.    }
    89.  
    90.    static int sem_wait(int sem_set_id)
    91.    {
    92.       /* structure for semaphore operations.   */
    93.       struct sembuf sem_op;
    94.  
    95.       /* wait on the semaphore, unless it's value is non-negative. */
    96.       sem_op.sem_num = 0;
    97.       sem_op.sem_op = -1;
    98.       sem_op.sem_flg = IPC_NOWAIT;
    99.       return semop(sem_set_id, &sem_op, 1);
    100.    }
    101. };
    102.  
    103. ///Constructor
    104. VideoModel::VideoModel():m_BufferSize(0),m_ShmKey(0),m_SemKey(0),m_Res(0,0),m_pTimer(0),m_PreviewState(false),
    105. m_Attached(false)
    106. {
    107.    VideoInterface& interface = VideoInterfaceSingleton::getInstance();
    108.    connect( &interface , SIGNAL(receivingEvent(int,int,int,int,int) ), this, SLOT( receivingEvent(int,int,int,int,int) ));
    109.    connect( &interface , SIGNAL(deviceEvent()                       ), this, SLOT( deviceEvent()                       ));
    110.    connect( &interface , SIGNAL(stoppedReceivingEvent(int,int)      ), this, SLOT( stoppedReceivingEvent(int,int)      ));
    111. }
    112.  
    113. ///Singleton
    114. VideoModel* VideoModel::getInstance()
    115. {
    116.    if (!m_spInstance) {
    117.       m_spInstance = new VideoModel();
    118.    }
    119.    return m_spInstance;
    120. }
    121.  
    122. ///Stop video preview
    123. void VideoModel::stopPreview()
    124. {
    125.    VideoInterface& interface = VideoInterfaceSingleton::getInstance();
    126.    interface.stopPreview();
    127.    m_PreviewState = false;
    128.    if (m_pTimer)
    129.       m_pTimer->stop();
    130.    if (m_Attached) {
    131.       ShmManager::detachShm((char*)m_pBuffer);
    132.       m_Attached = false;
    133.    }
    134. }
    135.  
    136. ///Start video preview
    137. void VideoModel::startPreview()
    138. {
    139.    if (m_PreviewState) return;
    140.    VideoInterface& interface = VideoInterfaceSingleton::getInstance();
    141.    QDBusPendingReply<int,int,int,int,int> reply = interface.startPreview();
    142.    reply.waitForFinished();
    143.    if (!reply.isError()) {
    144.       m_Res.width   = reply.argumentAt(0).toInt();
    145.       m_Res.height  = reply.argumentAt(1).toInt();
    146.       m_ShmKey      = reply.argumentAt(2).toInt();
    147.       m_SemKey      = reply.argumentAt(3).toInt();
    148.       m_BufferSize  = reply.argumentAt(4).toInt();
    149.       if (!m_pTimer) {
    150.          m_pTimer = new QTimer(this);
    151.          connect(m_pTimer,SIGNAL(timeout()),this,SLOT(timedEvents()));
    152.       }
    153.       m_pTimer->setInterval(42);
    154.       m_pTimer->start();
    155.       m_PreviewState = true;
    156.    }
    157. }
    158.  
    159. bool VideoModel::isPreviewing()
    160. {
    161.    return m_PreviewState;
    162. }
    163.  
    164. ///@todo Set the video buffer size
    165. void VideoModel::setBufferSize(uint size)
    166. {
    167.    m_BufferSize = size;
    168. }
    169.  
    170. ///Event callback
    171. void VideoModel::receivingEvent(int shmKey, int semKey, int videoBufferSize, int destWidth, int destHeight)
    172. {
    173.    m_ShmKey     = (uint)shmKey;
    174.    m_ShmKey     = (uint)semKey;
    175.    m_BufferSize = videoBufferSize;
    176.    m_Res.width  = destWidth;
    177.    m_Res.height = destHeight;
    178.  
    179.  
    180. }
    181.  
    182. ///Callback when video is stopped
    183. void VideoModel::stoppedReceivingEvent(int shmKey, int semKey)
    184. {
    185.    m_ShmKey = (uint)shmKey;
    186.    m_ShmKey = (uint)semKey;
    187. }
    188.  
    189. ///Event callback
    190. void VideoModel::deviceEvent()
    191. {
    192.  
    193. }
    194.  
    195. ///Update the buffer
    196. void VideoModel::timedEvents()
    197. {
    198.    if ( !m_Attached ) {
    199.       int shm_id = ShmManager::getShm(m_BufferSize, m_ShmKey);
    200.       m_pBuffer  = ShmManager::attachShm(shm_id);
    201.       m_Attached = true;
    202.       m_SetSetId = ShmManager::get_sem_set(m_SemKey);
    203.    }
    204.  
    205.    int ret = ShmManager::sem_wait(m_SetSetId);
    206.    if (ret != -1) {
    207.       qDebug() << "Updating frame" << m_pBuffer << m_Res.width << m_Res.height << m_BufferSize;;
    208.       QByteArray array((char*)m_pBuffer,m_BufferSize);
    209.       m_Frame.resize(0);
    210.       m_Frame = array;
    211.       emit frameUpdated();
    212.    }
    213.    else {
    214.       qDebug() << "Skipping" << ret;
    215.       usleep(rand()%100000); //Be sure it can come back in sync
    216.    }
    217.    qDebug() << "Ret" << ret;
    218. }
    219.  
    220. ///Return the current framerate
    221. QByteArray VideoModel::getCurrentFrame()
    222. {
    223.    return m_Frame;
    224. }
    225.  
    226. ///Return the current resolution
    227. Resolution VideoModel::getActiveResolution()
    228. {
    229.    return m_Res;
    230. }
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  2. 27th June 2012, 12:13 #2
    high_flyer
    high_flyer is offline Wiseguy
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    Default Re: Create video widget using byte array

    What is the original size of your frame?
    ==========================signature=============== ==================
    S.O.L.I.D principles (use them!):
    https://en.wikipedia.org/wiki/SOLID_...iented_design)

    Do you write clean code? - if you are TDD'ing then maybe, if not, your not writing clean code.
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