Windows 7 boot troubleshooting: Difference between revisions

From miki
Jump to navigation Jump to search
(Created page with "To tidy up. Info collecting when trying to P2V (Physical-2-Virtual) a native (physical) Windows 7 partition to a virtual disk image for VirtualBox. {{file|win7_P2V_links.txt}...")
 
 
(2 intermediate revisions by the same user not shown)
Line 1: Line 1:

The new Microsoft's flagship OS come with new features in boot, and now has '''plenty''' of different ways to fail at boot, each time with very cryptic and unhelpful messages. It is very easy to get these insulting messages for instance when you change your harddisk, or restore your Windows 7 backup in a different machine (possibly a virtual one). Here I list all the issues I encountered, and how I did solve them.

== Tools ==
=== bootrec ===
Use '''BootRec''' to fix issues in the following items [http://support.microsoft.com/kb/927392]:
* A master boot record (MBR)
* A boot sector
* A Boot Configuration Data (BCD) store

Simply boot Windows Recovery CD, and type at prompt:
<source lang=bash>
bootrec
</source>

== Errors ==
=== Corrupted / Missing Master Boot Record (MBR) ===
Typical error messages when the MBR is absent / corrupted:
<source lang=text>
Missing operating system
Error loading operating system
Invalid partition table
MBR Error 1
...
</source>

There are actually 2 possible way for corrupted MBR:
* Corrupted MBR code (detected by BIOS)
* Corrupted Partition Table (detected by MBR code)

The actual message may vary depending on the BIOS (corrupted MBR code), or the variant of MBR code installed on the disk. Note that the MBR works fine if GRUB shows up (even in rescue mode).

Solutions:
* Install new MBR - Windows<br/>Boot Windows Recovery CD, and open command prompt
<source lang=bash>
bootrec /fixmbr
</source>
* Install GRUB
<source lang=bash>
TBC
</source>
* Fix partition table
<source lang=bash>
TBC
</source>
* Set boot partition
<source lang=bash>
TBC
</source>

=== Corrupted / Missing Volume Boot Record (VBR) ===
TBC

=== Corrupted / Missing BOOT.INI ===
TBC

=== Corrupted / Missing \bcd Directory ===
Error:
<source lang=bash>
Windows Boot Manager

File: \Windows\system32\winload.exe
Status: 0xc000000e
Info: The selected entry could not be loaded because the applicationis missing or corrupt
</source>

Fix:
* Boot Windows Recovery Disk, let auto-repair run. You'd likely get another error afterwards (0x0000007B), see below.

=== BSOD 0x0000007B ===
Error: BSOD 0x0000007B, followed with error message
<source lang=text>
Windows Error Recovery
Windows failed to start. A recent hardware or software change might be the
cause.

[...]

Launch Startup Repair (recommended)
Start Windows Normally

[...]
</source>

This message is indicative that the kernel was not even loaded (no way to launch Safe Mode). It means that the BCD is missing or corrupted.

Fix:
* Launch startup repair (or use recovery dvd)
* Go to command prompt:
<source lang=bash>
bcdedit /export C:\BCD_Backup
ren C:\boot\BCD bcd.old
bootrec /rebuildbcd
</source>

=== Missing drivers ===
* Fix missing drivers (BSOD 0x0000007B) &mdash; Still within Windows Recovery CD, start '''regedit''':
<source lang=reg>
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0000]
"InfPath"="mshdc.inf"
"InfSection"="msahci_Inst"
"ProviderName"="Microsoft"
"DriverDateData"=hex:00,80,8c,a3,c5,94,c6,01
"DriverDate"="6-21-2006"
"DriverVersion"="6.1.7600.16385"
"MatchingDeviceId"="pci\\cc_010601"
"DriverDesc"="Standard AHCI 1.0 Serial ATA Controller"
"Migrated"=dword:00000001

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\Control\PnP]
"DisableCDDB"=-

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\services\atapi]
"Start"=dword:00000000

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\services\msahci]
"Start"=dword:00000000
</source>
* Boot and ***wait*** for all devices to be detected.
* '''DO NOT''' reboot when prompted, but instead start '''regedit''' again:
<source lang=reg>
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\Control\PnP]
"DisableCDDB"=-
</source>

== To tidy up ==

To tidy up. Info collecting when trying to P2V (Physical-2-Virtual) a native (physical) Windows 7 partition to a virtual disk image for VirtualBox.
To tidy up. Info collecting when trying to P2V (Physical-2-Virtual) a native (physical) Windows 7 partition to a virtual disk image for VirtualBox.



Latest revision as of 16:03, 8 June 2015

The new Microsoft's flagship OS come with new features in boot, and now has plenty of different ways to fail at boot, each time with very cryptic and unhelpful messages. It is very easy to get these insulting messages for instance when you change your harddisk, or restore your Windows 7 backup in a different machine (possibly a virtual one). Here I list all the issues I encountered, and how I did solve them.

Tools

bootrec

Use BootRec to fix issues in the following items [1]:

  • A master boot record (MBR)
  • A boot sector
  • A Boot Configuration Data (BCD) store

Simply boot Windows Recovery CD, and type at prompt:

bootrec

Errors

Corrupted / Missing Master Boot Record (MBR)

Typical error messages when the MBR is absent / corrupted:

Missing operating system
Error loading operating system
Invalid partition table
MBR Error 1
...

There are actually 2 possible way for corrupted MBR:

  • Corrupted MBR code (detected by BIOS)
  • Corrupted Partition Table (detected by MBR code)

The actual message may vary depending on the BIOS (corrupted MBR code), or the variant of MBR code installed on the disk. Note that the MBR works fine if GRUB shows up (even in rescue mode).

Solutions:

  • Install new MBR - Windows
    Boot Windows Recovery CD, and open command prompt
bootrec /fixmbr
  • Install GRUB
TBC
  • Fix partition table
TBC
  • Set boot partition
TBC

Corrupted / Missing Volume Boot Record (VBR)

TBC

Corrupted / Missing BOOT.INI

TBC

Corrupted / Missing \bcd Directory

Error:

      Windows Boot Manager

File: \Windows\system32\winload.exe
Status: 0xc000000e
Info: The selected entry could not be loaded because the applicationis missing or corrupt

Fix:

  • Boot Windows Recovery Disk, let auto-repair run. You'd likely get another error afterwards (0x0000007B), see below.

BSOD 0x0000007B

Error: BSOD 0x0000007B, followed with error message

       Windows Error Recovery
Windows failed to start. A recent hardware or software change might be the 
cause.

[...]

    Launch Startup Repair (recommended)
    Start Windows Normally

[...]

This message is indicative that the kernel was not even loaded (no way to launch Safe Mode). It means that the BCD is missing or corrupted.

Fix:

  • Launch startup repair (or use recovery dvd)
  • Go to command prompt:
bcdedit /export C:\BCD_Backup
ren C:\boot\BCD bcd.old
bootrec /rebuildbcd

Missing drivers

  • Fix missing drivers (BSOD 0x0000007B) — Still within Windows Recovery CD, start regedit:
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}\0000]
"InfPath"="mshdc.inf"
"InfSection"="msahci_Inst"
"ProviderName"="Microsoft"
"DriverDateData"=hex:00,80,8c,a3,c5,94,c6,01
"DriverDate"="6-21-2006"
"DriverVersion"="6.1.7600.16385"
"MatchingDeviceId"="pci\\cc_010601"
"DriverDesc"="Standard AHCI 1.0 Serial ATA Controller"
"Migrated"=dword:00000001

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\Control\PnP]
"DisableCDDB"=-

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\services\atapi]
"Start"=dword:00000000

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\services\msahci]
"Start"=dword:00000000
  • Boot and ***wait*** for all devices to be detected.
  • DO NOT reboot when prompted, but instead start regedit again:
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\nxl_SYSTEM\ControlSet001\Control\PnP]
"DisableCDDB"=-

To tidy up

To tidy up. Info collecting when trying to P2V (Physical-2-Virtual) a native (physical) Windows 7 partition to a virtual disk image for VirtualBox.

win7_P2V_links.txt

Error 0x0000007B INACCESSIBLE_BOOT_DEVICE

    http://triplescomputers.com/blog/casestudies/stop-error-0x0000007b-0xfffff880009a98e8-0xffffffffc000000d-0x0000000000000000-0x0000000000000000/
    --> script to completely rebuild the BCD store using bcdedit.exe

    http://support.microsoft.com/kb/927391

    msg "The Windows Boot Configuration Data file is missing required information"

      - The Windows Boot Manager (Bootmgr) entry is not present in the Boot Configuration Data (BCD) store.
      - The Boot\BCD file on the active partition is damaged or missing.

    --> script to rebuild using bootrec.exe

        Bcdedit /export C:\BCD_Backup
        ren c:\boot\bcd bcd.old
        Bootrec /rebuildbcd

        (+also all bootec /fixmbr; bootrec /fixboot)

    --> script to rebuild using bcdedit.exe (if previous one fails)

    http://social.technet.microsoft.com/Forums/en-US/windowsbackup/thread/b4d45d9d-4c90-4ab0-ae38-f1257ce9c608/
    --> About Bare Metal Restore (=P2V)
    --> About no injecting driver during Bare Metal Restore (BMR) recovery (DWORD DoNOtINjectDrivers)
    --> About modifying drivers intelide / Pcide
        ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

        VMWare VM:
         aliide 3
         amdide 3
        atapi 0
         cmdide 3
         iastorv 3
        intelide 0
         msahci 3
         pciide 3
         viaide 3
        LSI_SAS 0

        Dell PE2970 physical machine with RAID card:
         aliide 3
         amdide 3
        atapi 0
         cmdide 3
         iastorv 3
         intelide 3
        msahci 0
         pciide 3
         viaide 3
         LSI_SAS 3

        Dell PET100 physical machine on native SATA adapter:
         aliide 3
         amdide 3
        atapi 0
         cmdide 3
         iastorv 3
         intelide 3
        msahci 0
        pciide 0
         viaide 3
         LSI_SAS 3

        Win 7 64x custom built physical machine on native SATA adapter:
         aliide 3
         amdide 3
        atapi 0
         cmdide 3
         iastorv 3
         intelide 3
        msahci 0
        pciide 0
         viaide 3
         LSI_SAS 3

    (+idem for LSI_SAS2)

    (P2V for Windows is called BMR apparently)

    http://reboot.pro/topic/14130-bsod-7b-finally-fixed-for-me-maybe-for-you-too/
    --> ***EXCELLENT*** analysis on the boot process in windows. A MUST READ!!!

P2V using VMware vCenter Converter
    http://www.sysprobs.com/physical-virtual-machine-vmware-vcenter-converter
    --> guide


NTFS on linux
    http://www.tuxera.com/community/ntfs-3g-advanced/
    --> ntfs-3g advanced guide

    http://jp-andre.pagesperso-orange.fr/advanced-ntfs-3g.html
    http://jp-andre.pagesperso-orange.fr/permissions.html
    --> detailed information

    http://jp-andre.pagesperso-orange.fr/advanced-ntfs-3g.html
    --> tools.zip, that contains ntfscp.sh, a script that copy directory and keep permissions
        To copy, while copy permission use ntfscp.sh

        Note that I don't need that to copy registry from one disk to another
        (Simpler is to boot in Win7, and copy using Windows Explorer)

    http://b.andre.pagesperso-orange.fr/extend-attr.html
    --> More info on NTFS extended attributes (stored as ntfs stream, containing special permission
    --> these attributes are copied by ntfscp.sh (and also ntfscp itself I think)
    --> However I can't make cp, tar or rsync copy these xattr

    http://tuxera.com/forum/viewtopic.php?f=2&t=29567
    --> Copying Between NTFSes With Preserving Permissions



Linux HW misc
    sudo lshw -class disk         # view all disks
    sudo parted -l                # view all partitions
    ls /sys/block/sd*/            # view all partitions

Windows Registry

    http://support.microsoft.com/kb/100010

    --> What are Control Sets? What is CurrentControlSet?

        About ControlSet001 = usually default, and COntrolSet002, usually last known good
        About key Select, with values Current, Default, Failed, LastKnownGood

    http://msdn.microsoft.com/en-us/library/windows/hardware/ff546173(v=vs.85).aspx

    --> About CurrentControlSet\Enum

        PnP manager creates a subkey for each device

    http://diddy.boot-land.net/firadisk/files/mounteddevices.htm

    --> About SYSTEM\MountedDevices

        should be deleted when booting on different devices (Windows will reconstruct it).
        Otherwise disk will be assigned a different letter (it is safe to delete values '\??\Volumne{guid}')

    http://technet.microsoft.com/en-us/library/cc957340.aspx
    --> Detailed description of SYSTEM registry, HKEY_LOCAL_MACHINE... (for Windows 2000)

    http://msdn.microsoft.com/en-us/library/windows/hardware/ff546165(v=vs.85).aspx
    --> Info on SYSTEM/CurrentCOntrolSet/Control
        Class       --> info about the device setup class (setup class like class installer, upper-filter drivers, lower-filter drivers)
        CoDeviceInstallers  --> class-specific co-installers
        DeviceClasses   --> subkey for each device interface class
    --> + info on Services/, on Enum/, on Hardware Profiles

    http://msdn.microsoft.com/en-us/library/windows/hardware/ff558808(v=vs.85).aspx
        The following keys are link to Pnp:
        Control/Class
        Control/DeviceClasses
        Enum
        Hardware Profiles


P2V - manual

    http://www.justsoftwaresolutions.co.uk/general/importing-windows-into-virtualbox.html

    About taking SYSTEM hive from a clean windows install in VM, and importing it in the P2V machine.
    About patching the SYSKEY (--> SYSTEM, SECURITY, SAM protected by checksum)

    http://www.beginningtoseethelight.org/ntsecurity/index.htm

    --> very detailed info on windows security, on Security Accounts Manager (SAM file), data structure, relationships, etc.

VirtualBox documentation

    http://www.virtualbox.org/manual/ch05.html
    --> About virtual storage
        - SATA: better than IDE, but only available since Vista w/o additional drivers
                standard interface for SATA control = AHCI (Advanced Host Controller Interface)

        - SAS = Serial Attached SCSI.
                VM emulates it as a LSI Logic SAS control (require Windows Vista or higher, or additional drivers in XP)


Windows Boot issue

    https://forums.virtualbox.org/viewtopic.php?f=7&t=24209&p=107595

    --> About "A disk read error occured\nPress Ctrl-Alt-Del to restart"

        Error comes from the Volume Boot Record, info on disk geometry is wrong (trying to read a bad sector, or a 
        sector number that does not exist on the drive). So message is printed by BIOS, from call in the MBR code

        See detailed explanation at http://www.xtralogic.com/support.shtml#faq_vhdu_disk_read_error

        Fix is to us TESTDISK to fix the volume boot record (see http://www.xtralogic.com/testdisk_rebuild_bootsector.shtml)

    http://en.wikipedia.org/wiki/Volume_boot_record
    --> Info on VBR


    http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006556
    --> VMWare KB. List of all boot issues (and error messages), and how to fix them. But usually requires
        using repair disk (no real explanations of what to do)
    --> However lots of info, + links to other pages

    http://support.microsoft.com/kb/308041
    --> Advanced troubleshooting for general startup problems in Windows XP
        Several steps, things to try, etc
        Not much technical things, but some pointers

    http://support.microsoft.com/kb/314477
    -->  Error message: "Windows could not start because of a computer disk hardware configuration problem"

    about message
        Windows could not start because of a computer disk hardware configuration problem.

         Could not read from the selected boot disk. Check boot path and disk hardware.

         Please check the Windows documentation about hardware disk configuration and your hardware reference manuals for additional information.

    Due to wrong Boot.ini file (wrong partition selected in Boot.ini (partition does not exist))

    http://www.sevenforums.com/tutorials/219533-troubleshooting-windows-7-failure-boot.html
    --> yet another comprehensive list on boot issues, but w/o explanation. Only using 3rd party tools
    
Admin password recovery

    http://social.microsoft.com/Forums/en-US/studentrockstar/thread/bd195503-06ab-47a7-b941-f5fe2c2215bb

    Using loophole during Windows reinstall (install files, then press Shift-F10 after 1st reboot)

Copy with rsync, keeping permissions:

    https://mebsd.com/cli-commands/rsync-over-ssh-keeping-file-ownerships-and-permissions.html

    --> Copy using rsync, keeping permissions
        Fix sudoers: add

        ssh-user        ALL = NOPASSWD: /usr/local/rsync

        then
        rsync -a --rsync-path="sudo rsync" /usr/local/www ssh-user@backup-server.tld:/usr/backup_dir/

Remove Bit-Locker Encryption

    http://social.technet.microsoft.com/Forums/en-US/winserversecurity/thread/74783472-3776-4b9e-a8f4-7ab777bd99d9/

    --> About removing BDEDrive after BL was disabled for C:

        bcdboot c:\windows /s c:
        Then set c: as active 

        Question: What difference between this bcdboot command, and command bootrec above to repair a bad BCD?
        Anyway I used that and it works

    http://technet.microsoft.com/en-us/library/cc731894.aspx#BKMK_WINUI

    --> About disk management on Windows 7

        Namely how to shrink partition from command-line (using DISKPART), or from gui
        Must remove restore points, cache file, hibernat.sys file, etc

        Still the best is to use ntfsresize (that's what I did and it worked flawless')

    http://technet.microsoft.com/en-us/library/cc732774.aspx
    
    --> Overview on BitLocker

    http://technet.microsoft.com/en-us/library/ee424315(v=ws.10).aspx

    --> How to turn off bitlocker

        o Click Start, click Control Panel, click System and Security, and then click BitLocker Drive Encryption.
        o Find the drive on which you want BitLocker Drive Encryption turned off, and click Turn Off BitLocker.
        o A message is displayed, informing you that the drive will be decrypted and that decryption may take some time. Click Decrypt the drive to continue and turn off BitLocker on the drive.

        That's what I did, work very well

    http://www.howtogeek.com/howto/3187/disable-system-restore-in-windows-7/

    --> Disable windows restore

        Go to control panel, --> System --> System protection --> Configure... --> Turn off system protection
        (one can also reduce space used by system restore)
    

    Best to do before shrink a drive:
    - remove / disable windows restore
    - remove cache file
    - remove hibernat file
    - empty recycle bin
    - boot in linux, check that System Volume Information is indeed empty


Virtualbox IO APIC

    https://forums.virtualbox.org/viewtopic.php?f=9&t=21480

    --> how to disable IO APIC after installing windows 7. But I read somewhere that IO APIC is mandatory for 64-bit.

Virtualbox P2V

    --> use immutable mode while trying P2V, so that we can always revert (works for RAW image too)

    http://www.rajatarya.com/website/taming-windows-virtualbox-vm

    --> About RAW mode. Suggest to use custom mbr as in my notes, etc. + repair of windows

        In the comments, script to create grub rescue iso:

        #create a grub CD image
        sudo install xorriso
        grub-mkrescue ?modules=?linux ext2 fat fshelp ls boot pc ntfs? ?output=/home/myusernam/virtualbox/grub2.iso iso/
        
        Also, another script to boot virtualbox as a separate user, who will have write access to disk device (because very bad idea to give world write access to /dev/sd*)
        Very complex script, not sure it is useful (won't solve my audio problem it seems')

Virtualbox P2V - boot issue

    If can't access safe mode (with list of drivers being loaded), then it is not a driver issue, but instead a MBR / VBR / Boot.ini issue (still might result into 0x7B error or various error messages)

    If we see safe mode list, and get 0x7B before login screen, then that's clearly a driver issue / registry setting issue.
    Replacing SYSTEM hive with another one from working VM should give access to login screen

    If go to login screen, but reboot
    Possible corrupted SYSTEM / SECURITY / SAM. Pick consistency set, and see if that boots

    etc.

    http://r3dux.org/2010/01/how-to-switch-a-virtualbox-windows-guest-hard-drive-from-ide-to-sata-mode/

    --> About switching from IDE to SATA

        On Windows 7, easiest is to add SATA controller, boot, have windows install the driver for it (on XP, require intel matrix driver), then uninstall it, reboot, etc

    http://communities.vmware.com/message/2030146

    --> Famous comment about setting driver at boot in registry service key
        Basically, load remote HIVE SYSTEM, then edit as follows (0 means loaded at boot, required for windows to see the drive)

            Aliide = 3
            Amdide =3
            Atapi = 0
            Cmdide = 3
            iaStorV = 3
            intelide = 0
            msahci = 3
            pciide = 3
            viaide = 3
            LSI_SAS = 0
            (some say also for LSI_SAS2)

        In my case, this was not enough (had the extra setting in PnP + wrong Class/, wrong enum/ etc). Also I only use SATA, so I don't need LSI_SAS, etc
    
    http://kb.vmware.com/selfservice/microsites/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=1005208
    --> Injecting SCSI controller device drivers into Windows when it fails to boot after converting it with VMware Converter (1005208)

        Idem, about setting LSI_SAS to 0 (+ check that C:\Windows\System32\Drivers contains lsi_sas.sys)

    http://blogs.technet.com/b/markrussinovich/archive/2011/11/08/3463572.aspx

    --> About disk ID, disk signature collision, solve it by forcing online, how to use DISKPART to restore the old disk ID reference in BCD hive, etc. A must read
        if disk ID not found, error 0x0000000e

        Note that DISKPART can be used to put disk online using the CLI


Other links:
http://support.microsoft.com/kb/314082
http://support.microsoft.com/kb/922976
http://www.justandrew.net/2009/10/stop-0x0000007b-on-p2vd-windows-7.html
http://web2.minasi.com/forum/topic.asp?TOPIC_ID=31980
https://docs.google.com/document/d/1UFmoqJsQPO7p98Bv743xNsIF6BsdZruiJFkd3cqlb7A/edit?pli=1
http://www.registryonwindows.com/registry-security-2.php
http://technet.microsoft.com/en-us/library/bb457006.aspx
http://technet.microsoft.com/en-us/library/cc770856.aspx
http://www.gohacking.com/how-windows-product-activation-works/


WIndows 7 tips

    psexec -i -d -s c:\windows\regedit.exe
    --> very handy to see keys that otherwise are not shown in regedit (and also to ease access to some keys - I only need to change ownership once)

Linus tips

    # To copy dd over ssh, simply pipe through ssh of course!!!
    dd if=/dev/sda7 | ssh backupserver dd of=/backup/sda7.img

    # Note that using scp does not work
    # Alternative is to use regular 'cat /dev/sda' or 'cat > /dev/sda'


    # To debug permission issues, find PID of faulty program (e.g. courier), then
    strace -fp <pid>

    # ... and then trigger action that cause the permission issue, and see the log above


    # Simple shred (too pass over sdb - can also shred a file, but some limitation, see man page)
    sudo shred -n2 -v /dev/sdb 

    # Other: wipe, or D-BAN (http://www.dban.org/)


    # Network tools (from http://www.howtogeek.com/108511/how-to-work-with-the-network-from-the-linux-terminal-11-commands-you-need-to-know/)

    curl & wget
    ping
    tracepath (similar to traceroute but does not require root privilege)
    mtr (ping and tracepath together, identify at which hop packets are lost)
    host (DNS lookups and reverse lookups)
    whois
    ifplugstatus
    ifconfig
    ifdown   (same as ifconfig down)  -- NOT ALLOWED WITH NETWORK-MANAGER
    ifup (same as ifconfig up)  -- NOT ALLOWED WITH NETWORK-MANAGER
    sudo dhclient -r   # release dhcp lease
    sudo dhclient     # get new lease
    netstat
    netstat -s     # view detailed stat on each interface

1080i vs 1080p

    http://www.howtogeek.com/132486/what-is-the-difference-between-1080p-and-1080i/