Repairing a GoPro Hero Video

GoPro Hero

{< table "table-hover table-striped" >} ||| |-|-| | Operating System | Mac OS X
Linux | | Website | GoPro Website | | Last Update | 12/09/2012 |

Introduction

If you have a GoPro camera or another device that records MP4 videos and for some unexpected reason your video is corrupted for various reasons, it's possible to recover the video without sound! It's not ideal, but it's better than losing everything.

First, reinsert the card into the device and see if it can repair it by itself. An SOS message will appear, press any other button to let it attempt the repair. If it doesn't work... continue with the following steps.

Prerequisites

You will need:

Perl (>= 5.8)
A repair script ^1

Repair Script

Here is the downloadable version above, but if you want to see its content:

(fix.pl)

#!/usr/bin/perl
my $infile = shift(@ARGV);
my $outfile = $infile . ".restore.mp4";

my $ctts_offset=0;
my $width = 1280;
my $height = 720;
my $framerate = 25;
my $i, $val;

#
# Parse command line options for options
#
for($i=0; $i<@ARGV; $i++) {
    if ($ARGV[$i] =~ /-ctts/) {
        $ctts_offset = $ARGV[++$i];
    }
    if ($ARGV[$i] =~ /-reso/){
        $val = $ARGV[++$i];
        if ($val eq '720p30' || $val eq 'ntscr2') {
            $width = 1280;
            $height = 720;
            $framerate = 30;
        } elsif ($val eq '720p60' || $val eq 'ntscr3') {
            $width = 1280;
            $height = 720;
            $framerate = 60;
        } elsif ($val eq '960p30' || $val eq 'ntscr4') {
            $width = 1280;
            $height = 960;
            $framerate = 30;
        } elsif ($val eq '1080p30' || $val eq 'ntscr5') {
            $width = 1920;
            $height = 1080;
            $framerate = 30;
        } elsif ($val eq '480p60' || $val eq 'ntscr1') {
            $width = 848;
            $height = 480;
            $framerate = 60;
        } elsif ($val eq '720p60' || $val eq 'palr3') {
            $width = 1280;
            $height = 720;
            $framerate = 50;
        } elsif ($val eq '960p30' || $val eq 'palr4') {
            $width = 1280;
            $height = 960;
            $framerate = 25;
        } elsif ($val eq '1080p30' || $val eq 'palr5') {
            $width = 1920;
            $height = 1080;
            $framerate = 25;
        } elsif ($val eq '480p60' || $val eq 'palr1') {
            $width = 848;
            $height = 480;
            $framerate = 50;
        } elsif ($val eq '720p30' || $val eq 'palr2') {
            $width = 1280;
            $height = 720;
            $framerate = 25;
        } elsif ($val eq '960p48' || $val eq '96048HD2') {
            $width = 1280;
            $height = 960;
            $framerate = 48;    
        } else {
            printf("Error - resolution $val not supported. Trying default ".$height."p"."$framerate\n");
        }
    }

}

open INFILE, "<", $infile or die("Cannot open $infile for reading\n");
binmode INFILE;


print ("\nAttempting to fix $infile\n\n");

#disable screen buffering
$|=1;

#
# read data section, find video frames
#

my $n, $size, $type, $buff, $framecount, @ptrs, @szs, $offset, $pmdat;

#
# Skip looking for mdat, find frames by brute force
#


$framecount = 0;

#set delimiter to look for 6-byte value indicating AVC frame start
$/ = pack ("C*", (0x00, 0x00, 0x00, 0x02, 0x09));

printf("Found frame        at         "); 
while ($buff = <INFILE>)  {
    printf("\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b%06d at %08x", $framecount, (tell INFILE) - 5);
    $ptrs[$framecount] = (tell INFILE)-5; #adjust to start of code
    if ($framecount > 0) {
        $szs[$framecount-1] = $ptrs[$framecount] - $ptrs[$framecount-1];
        #print ("size:  ".$szs[$framecount-1]."  \n");
    }
    $framecount++;
}

# throw away last one since it triggered on EOF
$framecount--;
pop(@ptrs);

#set beginning of mdat pointer based on 1st found frame
$pmdat=$ptrs[0]-8;


if ($framecount == 0){
    printf("\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b");
    printf("No frames found. Quitting.            \n");
    close INFILE;
    exit;
} else {
    print ("\n");
}


open OUTFILE, ">", $outfile or die("Cannot open $outfile for writing\n");
binmode OUTFILE;
print ("Opened file $outfile for writing\n\n");


$min=0xffffffff;
$max=0x0;
foreach(@szs){
    if ($_ > $max) {$max = $_}
    if ($_ < $min) {$min = $_}
}


printf("Found %d (%x) frames, or approx %ds of video at %dfps\n", $framecount, $framecount, $framecount / $framerate, $framerate);
printf("   min size %x, max size %x\n", $min, $max);
printf("   from %x, to %x\n", $ptrs[0], $ptrs[$framecount-1]);



#
# Rebuild Header
#

my $hdrsize, $i, $moov, $stbl ;

#calculate size
#17 B per frame V, 17 Bpf A, plus overhead
$hdrsize = (34 * $framecount) + 2500;
$hdrsize = int ($hdrsize / 0x8000) + 1;
if ($hdrsize % 2 == 0) {
    $hdrsize ++; # always make header size an odd multiple of 0x8000
}
$hdrsize = $hdrsize * 0x8000;

# calculate adjustment for new header size
$offset = $hdrsize - $pmdat ;

printf("Calculated header size of 0x%x \n",$hdrsize); 
printf("Using ctts offset of $ctts_offset\n");
printf("Using $width x $height @ $framerate fps\n");

# ftyp
print OUTFILE pack("NA4A4NA4A4NN",0x20,'ftyp','avc1',0,'avc1','isom',0,0);

#stbl
$stbl = pack ("NA4NN",0xf9,'stsd',0,0x01); 
$stbl .= pack ("NA4NNNNNNnnNNNCCCA21C11CCC",0xe9,'avc1',0,1,0,0,0,0,$width,$height,0x480000,0x480000,0,0,1,0x15,'Ambarella AVC encoder',0,0,0,0,0,0,0,0,0,0,0,0x18,0xff,0xff);
$stbl .= pack ("NA4NN",0x10,'pasp',0,0);
$stbl .= pack ("NA4N8",0x28,'clap',$width,1,$height,1,0,1,0,1);
if ($height == 1080) {
    $stbl .= pack ("NA4N15C3",0x47,'avcC',0x014d0028,0xffe10030,0x274d0028,0x9a6280f0,0x044fcb80,0x8800001f,0x48000753,0x07430005, 0xb8e00019,0xbfd5de5c,0x686000b7,0x1c000337,0xfabbcb87,0xc2211458,0x01000428,0xee,0x3c,0x80);
} elsif ($height == 480) {
    $stbl .= pack ("NA4N15C3",0x47,'avcC',0x014d401e,0xffe10030,0x274d401e,0x9a6281a8,0x7b602200,0x7d200,0x03a981d0,0x8007a180, 0x0044aa57,0x7971a100,0x0f430000,0x8954aef2,0xe1f08845,0x16000000,0x01000428,0xee,0x3c,0x80);
} elsif ($height == 960) {
    $stbl .= pack ("NA4N15C3",0x47,'avcC',0x014d0028,0xffe10030,0x274d0028,0x9a6280a0,0x0f360220,0x7d20,0x1d4c1d,0x0c0016e3, 0x800066ff,0x577971a1,0x8002dc70,0x000cdfea,0xef2e1f08,0x84516000,0x01000428,0xee,0x3c,0x80);
}  else {
    $stbl .= pack ("NA4N15C3",0x47,'avcC',0x014d0028,0xffe10030,0x274d0028,0x9a6280a0,0x0b760220,0x7d20,0x1d4c1d,0x0c003d0a, 0x0112a9,0x5de5c686,0x1e8500,0x8954ae,0xf2e1f088,0x451e0000,0x01000428,0xee,0x3c,0x80);
}
$stbl .= pack ("NA4N3",0x14,'btrt',0,0,0);
$stbl .= pack ("NA4N4",0x18,'stts',0,1,$framecount,90090/$framerate);
$stbl .= pack ("NA4NN",8*$framecount  + 0x10, 'ctts', 0, $framecount); 
if ($height == 1080) {
    for ($i=0;$i < $framecount;$i++){
        $stbl .= pack ("NN",1,0x0bbb);
    }
} elsif ( $framerate == 60) {
    for ($i=$ctts_offset;$i < $framecount + $ctts_offset;$i++){
        if (($i  %6 == 0) || ($i %6 == 3)) {
            $stbl .= pack ("NN",1,0x1199);
        } elsif (($i  %6 == 1) || ($i %6 == 5)) {
            $stbl .= pack ("NN",1,1);
        } else {
            $stbl .= pack ("NN",1,0);
        }
    }
} else {
    for ($i=$ctts_offset;$i < $framecount + $ctts_offset;$i++){
        if ($i % 3 == 0) {
            $stbl .= pack ("NN",1,0x2331);
        } else {
            $stbl .= pack ("NN",1,0);
        }
    }
}
$stbl .= pack ("NA4N5",0x1c,'stsc',0,1,1,1,1);
$stbl .= pack ("NA4N3",4*$framecount + 0x14, 'stsz',0,0,$framecount);
for ($i=0;$i < $framecount;$i++){
    $stbl .= pack ("N",$szs[$i]);
}
$stbl .= pack ("NA4N2",4*$framecount + 0x10, 'stco',0,$framecount);
for ($i=0;$i < $framecount;$i++){
    $stbl .= pack ("N",$ptrs[$i] + $offset);
}
#fake stss because I don't know how to re-calculate it
$stbl .= pack ("NA4N3",0x14,'stss',0,1,1);
$stbl .= pack ("NA4N",$framecount + 0xc,'sdtp',0);
if ($height == 1080) {
    for ($i=0;$i < $framecount;$i++){
        $stbl .= pack ("C",0);
    }
} else {
    for ($i=0;$i < $framecount;$i++){
        if ($i % 3 == 0) {
            $stbl .= pack ("C",0);
        } else {
            $stbl .= pack ("C",0x08);
        }
    }
}
#moov
print OUTFILE pack("NA4",$hdrsize-0x20,'moov');
print OUTFILE pack ("NA4N25",0x6c,'mvhd',0,0,0,0x015f90,2700000 / $framerate / 0x1d * $framecount, 0x010000, 0x01000000, 0, 0, 0x010000,0,0,0,0x010000,0,0,0,0x40000000,0,0,0,0,0,0,3);
print OUTFILE pack ("NA4",0x180,'udta');
if ($height == 960) {
    print OUTFILE pack ("NA4N30",0x80,'AMBA',0x040003,0x01030f00,0x04,0x1776,0x02bf20,0xb71b00,0xb71b00,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0x0100);
} elsif ($height == 1080) {
    print OUTFILE pack ("NA4N30",0x80,'AMBA',0x100009,0x01010800,0x04,0x0bbb * (3-($framerate/30)),0x02bf20,0xb71b00,0xb71b00,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0x0100);
} else {
    print OUTFILE pack ("NA4N30",0x80,'AMBA',0x100009,0x01030f00,0x04,0x0bbb * (3-($framerate/30)),0x02bf20,0x7a1200,0x7a1200,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0x0100);
}
print OUTFILE pack ("NA4N60",0xf8,'free',(0)x60);
print OUTFILE pack ("NA4",0x16a + length($stbl), 'trak');
print OUTFILE pack ("NA4N19n4",0x5c,'tkhd',0x07,0,0,1,0,2700000 / $framerate / 0x1d * $framecount,0,0,0,0,0x10000,0,0,0,0x10000,0,0,0,0x40000000,$width,0,$height,0);
print OUTFILE pack ("NA4",0x24,'edts');
print OUTFILE pack ("NA4N5",0x1c,'elst',0,1,0x015f90 / 0x1d * $framecount, 90090/$framerate,0x10000);
print OUTFILE pack ("NA4",0x44, 'tapt');
print OUTFILE pack ("NA4Nn4",0x14,'clef',0,$width,0,$height,0);
print OUTFILE pack ("NA4Nn4",0x14,'prof',0,$width,0,$height,0);
print OUTFILE pack ("NA4Nn4",0x14,'enof',0,$width,0,$height,0);
print OUTFILE pack ("NA4", 0x9e + length($stbl), 'mdia');
print OUTFILE pack ("NA4N6", 0x20, 'mdhd', 0,0,0,0x015f90,0x015f90 / 0x1d * $framecount,0);
print OUTFILE pack ("NA4N2A4N3CA13", 0x2e, 'hdlr', 0,0, 'vide',0,0,0,0xd,'Ambarella AVC');
print OUTFILE pack ("NA4",0x48 + length ($stbl), 'minf');
print OUTFILE pack ("NA4N3", 0x14, 'vmhd', 1,0,0,);
print OUTFILE pack ("NA4",0x24,'dinf');
print OUTFILE pack ("NA4N2",0x1c,'dref',0,1);
print OUTFILE pack ("NA4N",0xc,'url ',1);
print OUTFILE pack ("NA4", 0x8+length($stbl),'stbl');
print OUTFILE $stbl;


print OUTFILE pack ("NA4",$hdrsize - tell OUTFILE, 'free');

for ($i=$hdrsize - tell OUTFILE; $i>0; $i--) {
    print OUTFILE pack ("C",0);
}

#
# Copy data over
#

print OUTFILE pack ("NA4",unpack ("%123d*" , pack( "d*", @szs)) + 13,'mdat');
seek INFILE, $pmdat + 8, 0;
$framecount=0;
printf("Copying  frame       ..."); 
while ($buff = <INFILE>)  {
    printf("\b\b\b\b\b\b\b\b\b%06d...", $framecount++);
    print OUTFILE $buff;
}
print("\nDone.\n");

close OUTFILE;
close INFILE;

Usage

Put the fix.pl file in the same folder as your corrupted/unreadable video. Then launch the script from the terminal like this:

perl ./fix.pl <video>.MP4 -reso <resolution> -ctts <value>

video: specify the name of the video file to repair
resolution: indicate if it's PAL or NTSC, followed by the resolution identifier (look behind the GoPro camera, there are r1, r2...). For NTSC in r3, it would be ntscr3.
possible resolutions: palr1, palr2, palr3, palr4, palr5, ntscr1, ntscr2, ntscr3, ntscr4, ntscr5 and 96048HD2
ctts: Start with 0, then increase by 1 if the video quality doesn't meet your expectations

For my part, I was able to recover a 1.4GB video like this:

> perl ./fix.pl GOPR0029.MP4 -reso palr2 -ctts 0

Attempting to fix GOPR0029.MP4

Found frame 027878 at 53fffffb
Opened file GOPR0029.MP4.restore.mp4 for writing

Found 27878 (6ce6) frames, or approx 1115s of video at 25fps
   min size d09, max size 4e3fa
   from 8004, to 53ffc644
Calculated header size of 0xf8000 
Using ctts offset of 0
Using 1280 x 720 @ 25 fps
Copying  frame 027878...
Done.

Unfortunately, the last few minutes that weren't written to the card are missing, and also the audio since it's not possible to recover the sound with this method.

Your working video will have the same name as the original in the same location where the video is located, with 'restore' added to the name.

Repairing a GoPro Hero Video

Introduction

Prerequisites

Repair Script

Usage

References