New video output driver: "vmem", for direct memory access.

Sometimes our list of video output modules is still not enough for an
external libvlc application with specific requirements. For instance, an
SDL application running in full screen cannot open a new window on Linux
(this is a known libSDL limitation). This vmem video output allows it to
asynchronously render the video into an SDL_Surface, with full locking.

Resolution or pitch changes are not supported yet. I'd advise against
them however, since they often require a full chroma unload/reload
operation, which is quite expensive.

I also believe this feature should be directly integrated into libvlc,
but I don't want to be too intrusive yet.

configure.ac

@@ -1205,7 +1205,7 @@ VLC_ADD_PLUGINS([converter_fixed mono])
 VLC_ADD_PLUGINS([trivial_resampler ugly_resampler])
 VLC_ADD_PLUGINS([trivial_channel_mixer trivial_mixer])
 VLC_ADD_PLUGINS([playlist export nsc xtag])
-VLC_ADD_PLUGINS([i420_rgb grey_yuv rawvideo blend scale image logo magnify puzzle colorthres])
+VLC_ADD_PLUGINS([i420_rgb grey_yuv rawvideo blend scale image vmem logo magnify puzzle colorthres])
 VLC_ADD_PLUGINS([wav araw subtitle vobsub adpcm a52sys dtssys au ty voc xa nuv smf])
 VLC_ADD_PLUGINS([access_directory access_file access_udp access_tcp])
 VLC_ADD_PLUGINS([access_http access_mms access_ftp access_rtmp])

modules/video_output/Modules.am

@@ -17,3 +17,5 @@ SOURCES_opengl = opengl.c
 SOURCES_opengllayer = opengllayer.m
 SOURCES_image = image.c
 SOURCES_directfb = directfb.c
+SOURCES_vmem = vmem.c
+

modules/video_output/vmem.c

+/*****************************************************************************
+ * vmem.c: memory video driver for vlc
+ *****************************************************************************
+ * Copyright (C) 2008 the VideoLAN team
+ * $Id$
+ *
+ * Authors: Sam Hocevar <sam@zoy.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+/*****************************************************************************
+ * Preamble
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <vlc/vlc.h>
+#include <vlc_vout.h>
+
+/*****************************************************************************
+ * Local prototypes
+ *****************************************************************************/
+static int  Create    ( vlc_object_t * );
+static void Destroy   ( vlc_object_t * );
+
+static int  Init          ( vout_thread_t * );
+static int  LockPicture   ( vout_thread_t *, picture_t * );
+static int  UnlockPicture ( vout_thread_t *, picture_t * );
+
+/*****************************************************************************
+ * Module descriptor
+ *****************************************************************************/
+#define T_WIDTH N_( "Width" )
+#define LT_WIDTH N_( "Video memory buffer width." )
+
+#define T_HEIGHT N_( "Height" )
+#define LT_HEIGHT N_( "Video memory buffer height." )
+
+#define T_PITCH N_( "Pitch" )
+#define LT_PITCH N_( "Video memory buffer pitch in bytes." )
+
+#define T_CHROMA N_( "Chroma" )
+#define LT_CHROMA N_( "Output chroma for the memory image as a 4-character " \
+                      "string, eg. \"RV32\"." )
+
+#define T_LOCK N_( "Lock function" )
+#define LT_LOCK N_( "Address of the locking callback function. This " \
+                    "function must return a valid memory address for use " \
+                    "by the video renderer." )
+
+#define T_UNLOCK N_( "Unlock function" )
+#define LT_UNLOCK N_( "Address of the unlocking callback function" )
+
+#define T_DATA N_( "Callback data" )
+#define LT_DATA N_( "Data for the locking and unlocking functions" )
+
+vlc_module_begin( );
+    set_description( _( "Video memory module" ) );
+    set_shortname( _("Video memory") );
+
+    set_category( CAT_VIDEO );
+    set_subcategory( SUBCAT_VIDEO_VOUT );
+    set_capability( "video output", 0 );
+
+    add_integer( "vmem-width", 320, NULL, T_WIDTH, LT_WIDTH, VLC_FALSE );
+    add_integer( "vmem-height", 200, NULL, T_HEIGHT, LT_HEIGHT, VLC_FALSE );
+    add_integer( "vmem-pitch", 640, NULL, T_PITCH, LT_PITCH, VLC_FALSE );
+    add_string( "vmem-chroma", "RV16", NULL, T_CHROMA, LT_CHROMA, VLC_TRUE );
+    add_string( "vmem-lock", "0", NULL, T_LOCK, LT_LOCK, VLC_TRUE );
+    add_string( "vmem-unlock", "0", NULL, T_UNLOCK, LT_UNLOCK, VLC_TRUE );
+    add_string( "vmem-data", "0", NULL, T_DATA, LT_DATA, VLC_TRUE );
+
+    set_callbacks( Create, Destroy );
+vlc_module_end();
+
+/*****************************************************************************
+ * vout_sys_t: video output descriptor
+ *****************************************************************************/
+struct vout_sys_t
+{
+    int i_width, i_height, i_pitch;
+
+    void * (*pf_lock) (void *);
+    void (*pf_unlock) (void *);
+    void *p_data;
+};
+
+/*****************************************************************************
+ * Create: allocates video thread
+ *****************************************************************************
+ * This function allocates and initializes a vout method.
+ *****************************************************************************/
+static int Create( vlc_object_t *p_this )
+{
+    vout_thread_t *p_vout = ( vout_thread_t * )p_this;
+
+    /* Allocate instance and initialize some members */
+    p_vout->p_sys = malloc( sizeof( vout_sys_t ) );
+    if( ! p_vout->p_sys )
+        return VLC_ENOMEM;
+
+    p_vout->pf_init = Init;
+    p_vout->pf_end = NULL;
+    p_vout->pf_manage = NULL;
+    p_vout->pf_render = NULL;
+    p_vout->pf_display = NULL;
+
+    return VLC_SUCCESS;
+}
+
+/*****************************************************************************
+ * Init: initialize video thread
+ *****************************************************************************/
+static int Init( vout_thread_t *p_vout )
+{
+    int i_index;
+    picture_t *p_pic;
+    char *psz_chroma, *psz_tmp;
+    int i_width, i_height, i_pitch, i_chroma;
+
+    i_width = config_GetInt( p_vout, "vmem-width" );
+    i_height = config_GetInt( p_vout, "vmem-height" );
+    i_pitch = config_GetInt( p_vout, "vmem-pitch" );
+
+    psz_chroma = config_GetPsz( p_vout, "vmem-chroma" );
+    if( psz_chroma )
+    {
+        if( strlen( psz_chroma ) < 4 )
+        {
+            msg_Err( p_vout, "vmem-chroma should be 4 characters long" );
+            return VLC_EGENERIC;
+        }
+        i_chroma = VLC_FOURCC( psz_chroma[0], psz_chroma[1],
+                               psz_chroma[2], psz_chroma[3] );
+        free( psz_chroma );
+    }
+    else
+    {
+        msg_Err( p_vout, "Cannot find chroma information." );
+        return VLC_EGENERIC;
+    }
+
+    psz_tmp = config_GetPsz( p_vout, "vmem-lock" );
+    p_vout->p_sys->pf_lock = (void * (*) (void *))(intptr_t)atoll( psz_tmp );
+    free( psz_tmp );
+
+    psz_tmp = config_GetPsz( p_vout, "vmem-unlock" );
+    p_vout->p_sys->pf_unlock = (void (*) (void *))(intptr_t)atoll( psz_tmp );
+    free( psz_tmp );
+
+    psz_tmp = config_GetPsz( p_vout, "vmem-data" );
+    p_vout->p_sys->p_data = (void *)(intptr_t)atoll( psz_tmp );
+    free( psz_tmp );
+
+    if( !p_vout->p_sys->pf_lock || !p_vout->p_sys->pf_unlock )
+    {
+        msg_Err( p_vout, "Invalid lock or unlock callbacks" );
+        return VLC_EGENERIC;
+    }
+
+    I_OUTPUTPICTURES = 0;
+
+    /* Initialize the output structure */
+    p_vout->output.i_chroma = i_chroma;
+    p_vout->output.pf_setpalette = NULL;
+    p_vout->output.i_width = i_width;
+    p_vout->output.i_height = i_height;
+    p_vout->output.i_aspect = p_vout->output.i_width
+                               * VOUT_ASPECT_FACTOR / p_vout->output.i_height;
+
+    /* Define the bitmasks */
+    switch( i_chroma )
+    {
+      case VLC_FOURCC( 'R','V','1','5' ):
+        p_vout->output.i_rmask = 0x001f;
+        p_vout->output.i_gmask = 0x03e0;
+        p_vout->output.i_bmask = 0x7c00;
+        break;
+
+      case VLC_FOURCC( 'R','V','1','6' ):
+        p_vout->output.i_rmask = 0x001f;
+        p_vout->output.i_gmask = 0x07e0;
+        p_vout->output.i_bmask = 0xf800;
+        break;
+
+      case VLC_FOURCC( 'R','V','2','4' ):
+        p_vout->output.i_rmask = 0xff0000;
+        p_vout->output.i_gmask = 0x00ff00;
+        p_vout->output.i_bmask = 0x0000ff;
+        break;
+
+      case VLC_FOURCC( 'R','V','3','2' ):
+        p_vout->output.i_rmask = 0xff0000;
+        p_vout->output.i_gmask = 0x00ff00;
+        p_vout->output.i_bmask = 0x0000ff;
+        break;
+    }
+
+    /* Try to initialize 1 direct buffer */
+    p_pic = NULL;
+
+    /* Find an empty picture slot */
+    for( i_index = 0 ; i_index < VOUT_MAX_PICTURES ; i_index++ )
+    {
+        if( p_vout->p_picture[ i_index ].i_status == FREE_PICTURE )
+        {
+            p_pic = p_vout->p_picture + i_index;
+            break;
+        }
+    }
+
+    /* Allocate the picture */
+    if( p_pic == NULL )
+    {
+        return VLC_SUCCESS;
+    }
+
+    vout_InitPicture( VLC_OBJECT(p_vout), p_pic, p_vout->output.i_chroma,
+                      p_vout->output.i_width, p_vout->output.i_height,
+                      p_vout->output.i_aspect );
+
+    p_pic->p->i_pitch = i_pitch;
+
+    p_pic->pf_lock = LockPicture;
+    p_pic->pf_unlock = UnlockPicture;
+
+    p_pic->i_status = DESTROYED_PICTURE;
+    p_pic->i_type   = DIRECT_PICTURE;
+
+    PP_OUTPUTPICTURE[ I_OUTPUTPICTURES ] = p_pic;
+
+    I_OUTPUTPICTURES++;
+
+    return VLC_SUCCESS;
+}
+
+/*****************************************************************************
+ * Destroy: destroy video thread
+ *****************************************************************************
+ * Terminate an output method created by Create
+ *****************************************************************************/
+static void Destroy( vlc_object_t *p_this )
+{
+    vout_thread_t *p_vout = ( vout_thread_t * )p_this;
+
+    /* Destroy structure */
+    free( p_vout->p_sys );
+}
+
+/*****************************************************************************
+ * LockPicture: lock a picture
+ *****************************************************************************
+ * This function locks the picture and prepares it for direct pixel access.
+ *****************************************************************************/
+static int LockPicture( vout_thread_t *p_vout, picture_t *p_pic )
+{
+    p_pic->p->p_pixels = p_vout->p_sys->pf_lock( p_vout->p_sys->p_data );
+
+    return VLC_SUCCESS;
+}
+
+/*****************************************************************************
+ * UnlockPicture: unlock a picture
+ *****************************************************************************
+ * This function unlocks a previously locked picture.
+ *****************************************************************************/
+static int UnlockPicture( vout_thread_t *p_vout, picture_t *p_pic )
+{
+    p_vout->p_sys->pf_unlock( p_vout->p_sys->p_data );
+
+    (void)p_pic;
+
+    return VLC_SUCCESS;
+}
+