diff --git a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.html b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.html
index 77995867..ae9341a2 100644
--- a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.html
+++ b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.html
@@ -88,14 +88,15 @@
       </cdk-virtual-scroll-viewport>
     </div>
     <div *ngIf="isShowSearch" class="search-result">
-      <cdk-virtual-scroll-viewport
-        #cvsvDeptSearchUser
-        itemSize="60"
+      <virtual-scroller
+        #vsDeptSearchUser
+        [items]="searchUserInfos"
         perfectScrollbar
         fxFlexFill
       >
         <ucap-profile-user-list-item
-          *cdkVirtualFor="let userInfo of searchUserInfos"
+          style="height: 60px;"
+          *ngFor="let userInfo of vsDeptSearchUser.viewPortItems"
           [userInfo]="userInfo"
           [checkable]="userInfo.seq !== loginRes.userSeq"
           [sessionVerinfo]="sessionVerinfo"
@@ -110,7 +111,7 @@
           matTooltipPosition="after"
         >
         </ucap-profile-user-list-item>
-      </cdk-virtual-scroll-viewport>
+      </virtual-scroller>
     </div>
   </div>
   <div *ngIf="!isUserSelect" class="btn-box">
diff --git a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.ts b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.ts
index 53a0765f..6ae7a8b2 100644
--- a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.ts
+++ b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/left-sidenav/organization.component.ts
@@ -66,6 +66,7 @@ import {
 } from '../../dialogs/organization/selected-user-list.dialog.component';
 import { TranslateService } from '@ngx-translate/core';
 import { StringFormatterPhonePipe } from 'projects/ucap-webmessenger-ui/src/lib/pipes/string.pipe';
+import { VirtualScrollerComponent } from 'ngx-virtual-scroller';
 
 @Component({
   selector: 'app-layout-chat-left-sidenav-organization',
@@ -120,8 +121,9 @@ export class OrganizationComponent
 
   @ViewChild('cvsvDeptUser', { static: false })
   cvsvDeptUser: CdkVirtualScrollViewport;
-  @ViewChild('cvsvDeptSearchUser', { static: false })
-  cvsvDeptSearchUser: CdkVirtualScrollViewport;
+
+  @ViewChild('vsDeptSearchUser', { static: false })
+  private vsDeptSearchUser: VirtualScrollerComponent;
 
   @ViewChild(PerfectScrollbarDirective, { static: false })
   psDirectiveRef?: PerfectScrollbarDirective;
@@ -306,8 +308,8 @@ export class OrganizationComponent
                   this.searchUserInfos = searchUserInfos;
                   this.selectedDepartmentProcessing = false;
 
-                  if (!!this.cvsvDeptSearchUser) {
-                    this.cvsvDeptSearchUser.scrollToOffset(0);
+                  if (!!this.vsDeptSearchUser) {
+                    this.vsDeptSearchUser.scrollToIndex(0);
                   }
                   if (!!this.psDirectiveRef) {
                     this.psDirectiveRef.update();
diff --git a/projects/ucap-webmessenger-app/src/app/layouts/messenger/messenger.layout.module.ts b/projects/ucap-webmessenger-app/src/app/layouts/messenger/messenger.layout.module.ts
index decd71d3..f390f876 100644
--- a/projects/ucap-webmessenger-app/src/app/layouts/messenger/messenger.layout.module.ts
+++ b/projects/ucap-webmessenger-app/src/app/layouts/messenger/messenger.layout.module.ts
@@ -39,6 +39,7 @@ import { MatListModule } from '@angular/material/list';
 import { MatChipsModule } from '@angular/material/chips';
 
 import { PerfectScrollbarModule } from 'ngx-perfect-scrollbar';
+import { VirtualScrollerModule } from 'ngx-virtual-scroller';
 
 import { TranslateModule } from '@ngx-translate/core';
 
@@ -93,6 +94,7 @@ import { DIALOGS } from './dialogs';
     MatSidenavModule,
 
     PerfectScrollbarModule,
+    VirtualScrollerModule,
 
     TranslateModule,
 
diff --git a/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.html b/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.html
index 3c3d3af3..3e789259 100644
--- a/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.html
+++ b/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.html
@@ -82,7 +82,9 @@
 </virtual-scroller>
 
 <div
-  #chatMessagesBuffer
+  #chatMessagesBufferContainer
   fxFlexFill
-  class="chat-messages-buffer disappear"
-></div>
+  class="chat-messages-buffer-container disappear"
+>
+  <div #chatMessagesBuffer fxFlexFill class="chat-messages-buffer"></div>
+</div>
diff --git a/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.scss b/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.scss
index 1178e2a9..974bb623 100644
--- a/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.scss
+++ b/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.scss
@@ -164,10 +164,12 @@ $tablet-l-width: 1024px;
   display: none !important;
 }
 
-.chat-messages-buffer {
+.chat-messages-buffer-container {
   position: absolute;
   top: 0px;
   overflow-y: hidden !important;
-  padding: 30px 40px;
+  padding: 2vh 2vw;
   flex-direction: column;
+  .chat-messages-buffer {
+  }
 }
diff --git a/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.ts b/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.ts
index 33993365..782e402c 100644
--- a/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.ts
+++ b/projects/ucap-webmessenger-ui-chat/src/lib/components/messages.component.ts
@@ -112,6 +112,9 @@ export class MessagesComponent implements OnInit, OnDestroy {
   @ViewChild('chatMessagesBuffer', { static: false })
   chatMessagesBuffer: ElementRef<HTMLElement>;
 
+  @ViewChild('chatMessagesBufferContainer', { static: false })
+  chatMessagesBufferContainer: ElementRef<HTMLElement>;
+
   @ViewChild(VirtualScrollerComponent, { static: false })
   private virtualScroller: VirtualScrollerComponent;
 
@@ -148,6 +151,7 @@ export class MessagesComponent implements OnInit, OnDestroy {
   readToHereEvent: Info<EventJson>;
   existReadToHereEvent = true;
   hidden = false;
+  swapped = false;
 
   constructor(
     private logger: NGXLogger,
@@ -393,13 +397,14 @@ export class MessagesComponent implements OnInit, OnDestroy {
     ];
   }
 
-  scrollTo(
+  swapScrollTo(
     to: Info<EventJson>,
     preCallback: () => void,
     postCallback: () => void,
-    useHide: boolean
+    useHide: boolean,
+    useSwap: boolean
   ) {
-    this.preSwapScroll(useHide);
+    this.preSwapScroll(useHide, useSwap);
     if (!!preCallback) {
       preCallback();
     }
@@ -408,19 +413,35 @@ export class MessagesComponent implements OnInit, OnDestroy {
         if (!!postCallback) {
           postCallback();
         }
-        this.postSwapScroll(useHide);
+        this.postSwapScroll(useHide, useSwap);
       });
     });
   }
 
-  preSwapScroll(useHide: boolean) {
+  preSwapScroll(useHide: boolean, useSwap: boolean) {
+    if (useSwap && !this.swapped) {
+      this.chatMessagesBuffer.nativeElement.innerHTML = this.chatMessagesContainer.nativeElement.innerHTML;
+      this.chatMessagesBuffer.nativeElement.scrollTop = this.chatMessagesContainer.nativeElement.scrollTop;
+      this.chatMessagesBufferContainer.nativeElement.classList.remove(
+        'disappear'
+      );
+      this.swapped = true;
+    }
+
     if (useHide && !this.hidden) {
       this.chatMessagesContainer.nativeElement.classList.add('hide');
       this.hidden = true;
     }
   }
 
-  postSwapScroll(useHide: boolean) {
+  postSwapScroll(useHide: boolean, useSwap: boolean) {
+    if (useSwap && this.swapped) {
+      this.chatMessagesBuffer.nativeElement.innerHTML = '';
+      this.chatMessagesBuffer.nativeElement.scrollTop = 0;
+      this.chatMessagesBufferContainer.nativeElement.classList.add('disappear');
+      this.swapped = false;
+    }
+
     if (useHide && this.hidden) {
       this.chatMessagesContainer.nativeElement.classList.remove('hide');
       this.hidden = false;
@@ -434,12 +455,13 @@ export class MessagesComponent implements OnInit, OnDestroy {
   scrollToBottom(): void {
     if (!!this.storedScrollItem) {
       if (!!this.readToHereEvent && this.firstCheckReadHere) {
-        this.scrollTo(
+        this.swapScrollTo(
           this.readToHereEvent,
           () => {},
           () => {
             this.firstCheckReadHere = false;
           },
+          true,
           true
         );
       } else {
@@ -447,13 +469,14 @@ export class MessagesComponent implements OnInit, OnDestroy {
           i => i.seq === this.storedScrollItem.seq
         );
 
-        this.scrollTo(
+        this.swapScrollTo(
           1 <= index ? this.eventList[index - 1] : this.eventList[0],
           () => {},
           () => {
             this.storedScrollItem = undefined;
           },
-          false
+          true,
+          true
         );
       }
     } else if (this.scrollUpInitalized) {
@@ -464,31 +487,34 @@ export class MessagesComponent implements OnInit, OnDestroy {
       }
     } else {
       if (!!this.readToHereEvent && this.firstCheckReadHere) {
-        this.scrollTo(
+        this.swapScrollTo(
           this.readToHereEvent,
           () => {},
           () => {
             this.firstCheckReadHere = false;
           },
-          true
+          true,
+          false
         );
       } else {
         if (
           this.virtualScroller.viewPortInfo.endIndex ===
           this.eventList.length - 2
         ) {
-          this.scrollTo(
+          this.swapScrollTo(
             this.eventList[this.eventList.length - 1],
             () => {},
             () => {},
+            true,
             false
           );
         } else {
-          this.scrollTo(
+          this.swapScrollTo(
             this.eventList[this.eventList.length - 1],
             () => {},
             () => {},
-            true
+            true,
+            false
           );
         }
       }
@@ -534,7 +560,7 @@ export class MessagesComponent implements OnInit, OnDestroy {
     if (this.scrollUpInitalized && this.eventRemained) {
       this.storeScrollPosition();
 
-      this.preSwapScroll(false);
+      this.preSwapScroll(true, true);
 
       this.moreEvent.emit(this.eventList[0].seq);
 
diff --git a/projects/ucap-webmessenger-ui-chat/src/lib/ucap-ui-chat.module.ts b/projects/ucap-webmessenger-ui-chat/src/lib/ucap-ui-chat.module.ts
index d1155ae9..6a096a94 100644
--- a/projects/ucap-webmessenger-ui-chat/src/lib/ucap-ui-chat.module.ts
+++ b/projects/ucap-webmessenger-ui-chat/src/lib/ucap-ui-chat.module.ts
@@ -4,9 +4,6 @@ import { FormsModule, ReactiveFormsModule } from '@angular/forms';
 
 import { FlexLayoutModule } from '@angular/flex-layout';
 
-import { ScrollingModule } from '@angular/cdk/scrolling';
-import { ScrollingModule as ExperimentalScrollingModule } from '@angular/cdk-experimental/scrolling';
-
 import { MatTooltipModule } from '@angular/material';
 import { MatFormFieldModule } from '@angular/material/form-field';
 import { MatIconModule } from '@angular/material/icon';
@@ -78,9 +75,6 @@ const PROVIDERS = [DatePipe];
     ReactiveFormsModule,
     FlexLayoutModule,
 
-    ScrollingModule,
-    ExperimentalScrollingModule,
-
     MatFormFieldModule,
     MatIconModule,
     MatInputModule,
diff --git a/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.html b/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.html
index e53a7a22..d09bda20 100644
--- a/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.html
+++ b/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.html
@@ -86,14 +86,22 @@
   </div>
   <div class="ucap-video-viewer-body">
     <div
+      #videoContainer
       class="ucap-video-viewer-video-icon"
       fxLayout="row"
       fxLayout.xs="column"
       fxLayoutAlign="center center"
     >
       <video
-        [src]="fileDownloadUrl"
         #audioPlayer
+        [src]="fileDownloadUrl"
+        [style.width]="'auto'"
+        [style.height]="
+          videoHeight > videoContainer.clientHeight
+            ? ((videoContainer.clientHeight - 20) / videoHeight) * videoHeight +
+              'px'
+            : videoHeight + 'px'
+        "
         (playing)="onPlayingVideo()"
         (pause)="onPauseVideo()"
         (timeupdate)="onTimeUpdateVideo()"
@@ -124,7 +132,7 @@
         fxLayout.xs="column"
       >
         <div class="ucap-video-viewer-video-time-current">
-          {{ currentTime | ucapSecondsToMinutes }}
+          {{ Math.floor(currentTime) | ucapSecondsToMinutes }}
         </div>
         <span class="ucap-video-viewer-spacer"></span>
         <button
@@ -148,7 +156,7 @@
         </button>
         <span class="ucap-video-viewer-spacer"></span>
         <div class="ucap-video-viewer-video-time-total">
-          {{ duration | ucapSecondsToMinutes }}
+          {{ Math.floor(duration) | ucapSecondsToMinutes }}
         </div>
       </div>
     </div>
diff --git a/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.ts b/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.ts
index de03c16e..a6c9c50c 100644
--- a/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.ts
+++ b/projects/ucap-webmessenger-ui/src/lib/components/file-viewer/video-viewer.component.ts
@@ -5,12 +5,14 @@ import {
   Output,
   EventEmitter,
   ViewChild,
-  ElementRef
+  ElementRef,
+  ChangeDetectorRef
 } from '@angular/core';
 import { ucapAnimations } from '../../animations';
 import { FileEventJson } from '@ucap-webmessenger/protocol-event';
 import { MatSlider, MatSliderChange } from '@angular/material';
 import { FileDownloadItem } from '@ucap-webmessenger/api';
+import { NGXLogger } from 'ngx-logger';
 
 @Component({
   selector: 'ucap-video-viewer',
@@ -38,13 +40,21 @@ export class VideoViewerComponent implements OnInit {
   timeSlider: MatSlider;
 
   playing = false;
-  duration = 0.01;
-  currentTime = 0;
+  duration = 0.0;
+  currentTime = 0.0;
   volume = 0.1;
   loading = false;
   fileDownloadItem: FileDownloadItem;
 
-  constructor() {}
+  videoWidth = 0;
+  videoHeight = 0;
+
+  Math = Math;
+
+  constructor(
+    private changeDetectorRef: ChangeDetectorRef,
+    private logger: NGXLogger
+  ) {}
 
   ngOnInit() {}
 
@@ -74,11 +84,11 @@ export class VideoViewerComponent implements OnInit {
   }
 
   onTimeUpdateVideo(): void {
-    this.currentTime = Math.floor(this.audioPlayer.nativeElement.currentTime);
+    this.currentTime = this.audioPlayer.nativeElement.currentTime;
   }
 
   onVolumeChangeVideo(): void {
-    this.volume = Math.floor(this.audioPlayer.nativeElement.volume);
+    this.volume = this.audioPlayer.nativeElement.volume;
   }
 
   onLoadStartVideo(): void {
@@ -87,7 +97,10 @@ export class VideoViewerComponent implements OnInit {
 
   onLoadedDataVideo(): void {
     this.loading = false;
-    this.duration = Math.floor(this.audioPlayer.nativeElement.duration);
+    this.duration = this.audioPlayer.nativeElement.duration;
+
+    this.videoWidth = this.audioPlayer.nativeElement.videoWidth;
+    this.videoHeight = this.audioPlayer.nativeElement.videoHeight;
   }
 
   onClickDownload(): void {