avsubtitleswriter/SubtitlesTextReader.m
/* |
File: SubtitlesTextReader.m |
Abstract: A class for reading subtitles text, in the form of an NSString. It will turn the text into CMSampleBufferRefs, and extract language code, extended language tag, and other metadata. See subtitles_text_en-US.txt for an example of the subtitles file format this class expects. |
Version: 1.0.1 |
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*/ |
#import "SubtitlesTextReader.h" |
#import <AVFoundation/AVFoundation.h> |
@interface Subtitle : NSObject |
+ (instancetype)subtitleWithText:(NSString *)text timeRange:(CMTimeRange)timeRange forced:(BOOL)forced; |
- (CMFormatDescriptionRef)copyFormatDescription; |
- (CMSampleBufferRef)copySampleBuffer; |
@property NSString *text; |
@property CMTimeRange timeRange; |
@property BOOL forced; |
@property CMTextDisplayFlags displayFlags; |
@end |
@implementation SubtitlesTextReader |
{ |
NSUInteger _index; |
NSArray *_subtitles; |
BOOL _wantsSDH; |
} |
- (instancetype)initWithText:(NSString *)text |
{ |
self = [super init]; |
if (self) |
{ |
_index = 0; |
if (text) |
{ |
NSMutableArray *mutableSubtitles = [NSMutableArray array]; |
// Check for a language |
NSRegularExpression *languageExpression = [NSRegularExpression regularExpressionWithPattern:@"language: (.*)" options:0 error:nil]; |
NSTextCheckingResult *languageResult = [languageExpression firstMatchInString:text options:0 range:NSMakeRange(0, [text length])]; |
_languageCode = [text substringWithRange:[languageResult rangeAtIndex:1]]; |
// Check for an extended language |
NSRegularExpression *extendedLanguageExpression = [NSRegularExpression regularExpressionWithPattern:@"extended language: (.*)" options:0 error:nil]; |
NSTextCheckingResult *extendedLanguageResult = [extendedLanguageExpression firstMatchInString:text options:0 range:NSMakeRange(0, [text length])]; |
_extendedLanguageTag = [text substringWithRange:[extendedLanguageResult rangeAtIndex:1]]; |
// See if SDH has been requested |
NSRegularExpression *characteristicsExpression = [NSRegularExpression regularExpressionWithPattern:@"characteristics:.*(SDH)" options:NSRegularExpressionCaseInsensitive error:nil]; |
NSTextCheckingResult *characteristicsResult = [characteristicsExpression firstMatchInString:text options:0 range:NSMakeRange(0, [text length])]; |
_wantsSDH = ([[text substringWithRange:[characteristicsResult rangeAtIndex:1]] caseInsensitiveCompare:@"SDH"] == NSOrderedSame) ? YES : NO; |
// Find the subtitle time ranges and text |
__block int forcedCount = 0; |
NSRegularExpression *subtitlesExpression = [NSRegularExpression regularExpressionWithPattern:@"(..):(..):(..),(...) --> (..):(..):(..),(...)( !!!)?\n(.*)" options:0 error:nil]; |
[subtitlesExpression enumerateMatchesInString:text options:0 range:NSMakeRange(0, [text length]) usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) { |
// Get the text |
NSString *subtitleText = [text substringWithRange:[result rangeAtIndex:10]]; |
// Create the time range |
double startTime = ([[text substringWithRange:[result rangeAtIndex:1]] doubleValue] * 60.0 * 60.0) + ([[text substringWithRange:[result rangeAtIndex:2]] doubleValue] * 60.0) + [[text substringWithRange:[result rangeAtIndex:3]] doubleValue] + ([[text substringWithRange:[result rangeAtIndex:4]] doubleValue] / 1000.0); |
double endTime = ([[text substringWithRange:[result rangeAtIndex:5]] doubleValue] * 60.0 * 60.0) + ([[text substringWithRange:[result rangeAtIndex:6]] doubleValue] * 60.0) + [[text substringWithRange:[result rangeAtIndex:7]] doubleValue] + ([[text substringWithRange:[result rangeAtIndex:8]] doubleValue] / 1000.0); |
CMTimeRange timeRange = CMTimeRangeMake(CMTimeMakeWithSeconds(startTime, 600), CMTimeMakeWithSeconds(endTime - startTime, 600)); |
// Is it forced? |
BOOL forced = NO; |
if (([result rangeAtIndex:9].length > 0) && [[text substringWithRange:[result rangeAtIndex:9]] isEqualToString:@" !!!"]) |
{ |
forced = YES; |
forcedCount++; |
} |
// Stash a Subtitle object for later use by -copyNextSampleBuffer |
[mutableSubtitles addObject:[Subtitle subtitleWithText:subtitleText timeRange:timeRange forced:forced]]; |
}]; |
// Set forced subtitles display flags as appropriate. |
if ([mutableSubtitles count] == forcedCount) |
{ |
for (Subtitle *subtitle in mutableSubtitles) |
{ |
subtitle.displayFlags = kCMTextDisplayFlag_forcedSubtitlesPresent | kCMTextDisplayFlag_allSubtitlesForced; |
} |
} |
else if (forcedCount > 0) |
{ |
for (Subtitle *subtitle in mutableSubtitles) |
{ |
subtitle.displayFlags = kCMTextDisplayFlag_forcedSubtitlesPresent; |
} |
} |
_subtitles = [mutableSubtitles copy]; |
} |
} |
return self; |
} |
+ (instancetype)subtitlesTextReaderWithText:(NSString *)text |
{ |
return [[[self class] alloc] initWithText:text]; |
} |
- (CMFormatDescriptionRef)copyFormatDescription |
{ |
// Take the format description from the first object. They are all the same since the display flag are all the same. |
return [[_subtitles firstObject] copyFormatDescription]; |
} |
- (NSArray *)metadata |
{ |
NSMutableArray *mutableMetadata = [NSMutableArray array]; |
// All subtitles must have the AVMediaCharacteristicTranscribesSpokenDialogForAccessibility characteristic. |
AVMutableMetadataItem *spokenItem = [AVMutableMetadataItem metadataItem]; |
[spokenItem setKey:AVMetadataQuickTimeUserDataKeyTaggedCharacteristic]; |
[spokenItem setKeySpace:AVMetadataKeySpaceQuickTimeUserData]; |
[spokenItem setValue:AVMediaCharacteristicTranscribesSpokenDialogForAccessibility]; |
[mutableMetadata addObject:spokenItem]; |
if (_wantsSDH) |
{ |
// SDH subtitles must also have the AVMediaCharacteristicDescribesMusicAndSoundForAccessibility characteristic. |
AVMutableMetadataItem *describesItem = [AVMutableMetadataItem metadataItem]; |
[describesItem setKey:AVMetadataQuickTimeUserDataKeyTaggedCharacteristic]; |
[describesItem setKeySpace:AVMetadataKeySpaceQuickTimeUserData]; |
[describesItem setValue:AVMediaCharacteristicDescribesMusicAndSoundForAccessibility]; |
[mutableMetadata addObject:describesItem]; |
} |
return [mutableMetadata copy]; |
} |
- (CMSampleBufferRef)copyNextSampleBuffer |
{ |
CMSampleBufferRef sampleBuffer = NULL; |
if (_index < _subtitles.count) |
{ |
sampleBuffer = [(Subtitle *)_subtitles[_index] copySampleBuffer]; |
_index++; |
} |
return sampleBuffer; |
} |
@end |
@implementation Subtitle |
+ (instancetype)subtitleWithText:(NSString *)text timeRange:(CMTimeRange)timeRange forced:(BOOL)forced |
{ |
Subtitle *subtitle = [[Subtitle alloc] init]; |
subtitle.text = text; |
subtitle.timeRange = timeRange; |
subtitle.forced = forced; |
return subtitle; |
} |
- (CMFormatDescriptionRef)copyFormatDescription |
{ |
// Create a subtitle 3g text format description with extensions |
NSDictionary *extensions = @{(id)kCMTextFormatDescriptionExtension_DisplayFlags : @(self.displayFlags), |
(id)kCMTextFormatDescriptionExtension_BackgroundColor : @{ |
(id)kCMTextFormatDescriptionColor_Red : @0, |
(id)kCMTextFormatDescriptionColor_Green : @0, |
(id)kCMTextFormatDescriptionColor_Blue : @0, |
(id)kCMTextFormatDescriptionColor_Alpha : @255}, |
(id)kCMTextFormatDescriptionExtension_DefaultTextBox : @{ |
(id)kCMTextFormatDescriptionRect_Top : @0, |
(id)kCMTextFormatDescriptionRect_Left : @0, |
(id)kCMTextFormatDescriptionRect_Bottom : @0, |
(id)kCMTextFormatDescriptionRect_Right : @0}, |
(id)kCMTextFormatDescriptionExtension_DefaultStyle : @{ |
(id)kCMTextFormatDescriptionStyle_StartChar : @0, |
(id)kCMTextFormatDescriptionStyle_EndChar : @0, |
(id)kCMTextFormatDescriptionStyle_Font : @1, |
(id)kCMTextFormatDescriptionStyle_FontFace : @0, |
(id)kCMTextFormatDescriptionStyle_ForegroundColor : @{ |
(id)kCMTextFormatDescriptionColor_Red : @255, |
(id)kCMTextFormatDescriptionColor_Green : @255, |
(id)kCMTextFormatDescriptionColor_Blue : @255, |
(id)kCMTextFormatDescriptionColor_Alpha : @255}, |
(id)kCMTextFormatDescriptionStyle_FontSize : @255}, |
(id)kCMTextFormatDescriptionExtension_HorizontalJustification : @0, |
(id)kCMTextFormatDescriptionExtension_VerticalJustification : @0, |
(id)kCMTextFormatDescriptionExtension_FontTable : @{@"1" : @"Sans-Serif"}}; |
CMFormatDescriptionRef formatDescription; |
CMFormatDescriptionCreate(NULL, kCMMediaType_Subtitle, kCMTextFormatType_3GText, (__bridge CFDictionaryRef)extensions, &formatDescription); |
return formatDescription; |
} |
- (CMSampleBufferRef)copySampleBuffer |
{ |
const char *text = self.text.UTF8String; |
// Setup the sample size |
uint16_t textLength = 0; |
size_t sampleSize = 0; |
if (text != NULL) |
textLength = strlen(text); // don't include terminator in the length |
sampleSize = textLength + sizeof(uint16_t); |
if (self.forced) |
sampleSize += (sizeof (uint32_t) * 2); // for the 'frcd' atom |
uint8_t *samplePtr = malloc(sampleSize); // malloc space for length of text, text, and extensions. This variable should be char *, uint8_t *, UInt8 * for byte alignment reasons. |
uint16_t textLengthBigEndian = CFSwapInt16HostToBig(textLength); |
memcpy(samplePtr, &textLengthBigEndian, sizeof(textLengthBigEndian)); |
if (textLength) |
memcpy ((samplePtr + sizeof(uint16_t)), text, textLength); |
uint8_t *ptr = samplePtr + sizeof (uint16_t) + textLength; |
if (self.forced) |
{ |
// Make room for the forced atom. |
(*(uint32_t *) ptr) = CFSwapInt32HostToBig((sizeof (uint32_t) * 2)); |
ptr += sizeof(uint32_t); |
// Set the forced atom. |
(*(uint32_t *) ptr) = CFSwapInt32HostToBig('frcd'); |
} |
CMBlockBufferRef dataBuffer; |
CMBlockBufferCreateWithMemoryBlock(kCFAllocatorDefault, samplePtr, sampleSize, kCFAllocatorMalloc, NULL, 0, sampleSize, 0, &dataBuffer); |
CMSampleTimingInfo sampleTiming; |
sampleTiming.duration = self.timeRange.duration; |
sampleTiming.presentationTimeStamp = self.timeRange.start; |
sampleTiming.decodeTimeStamp = kCMTimeInvalid; |
CMFormatDescriptionRef formatDescription = [self copyFormatDescription]; |
CMSampleBufferRef sampleBuffer; |
CMSampleBufferCreate(kCFAllocatorDefault, dataBuffer, true, NULL, 0, formatDescription, 1, 1, &sampleTiming, 1, &sampleSize, &sampleBuffer); |
if (formatDescription) |
CFRelease(formatDescription); |
if (dataBuffer) |
CFRelease(dataBuffer); |
return sampleBuffer; |
} |
@end |
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