[ID3 Dev] How do you know ID3 v1 without ID3v2

[hongyang]

thanks, Jim

I think that is to say the garbage data whould be not start with

$49 44 33 yy yy xx zz zz zz zz

is it true?



Jim 写道:
> If the header for the tag was properly written, you can check it using
> the pattern that Jud gave before:
>
> An ID3v2 tag can be detected with the following pattern:
> $49 44 33 yy yy xx zz zz zz zz
> Where yy is less than $FF, xx is the 'flags' byte and zz is less than $80.
>
>
> So, if the first 3 characters are "ID3", then check that the next two
> (yy) are less than $FF and that the last four (zz) are less than $80.
>
>
>
> hongyang wrote:
>   
>> Yes, you have my idea.
>>
>> I am also confused about that.
>>
>> garbage data would be start like "00 00 00 00 "chars and so on some "sync"
>>  pattern. but I am not confirm this.
>>
>>
>> Jim 写道:
>>     
>>> I might be confused but I think what he is asking is if a MP3 file that
>>> does not have an ID3v2 tag could somehow start with the characters "ID3".
>>>
>>> Or another way to say it is could there be "ID3" at the start of a MP3
>>> file but it is not a ID3v2 tag?
>>>
>>> I don't think this would happen but I also think that garbage data can
>>> sometimes appear at the beginning of an MP3 file.  So I don't think it
>>> is impossible.  I think that's why some players search for a certain
>>> "sync" pattern to identify the start of the real data.  Can someone
>>> confirm this?  (Or am I completely off on this?)
>>>
>>> Jim
>>>
>>>
>>>
>>>
>>> Jud White wrote:
>>>   
>>>       
>>>> No, frame headers would never start with ID3.
>>>>
>>>> hongyang wrote:
>>>>     
>>>>         
>>>>> Thanks,
>>>>>
>>>>> I think maybe you misunderstand me, I mean whether the situation could
>>>>> happen, the MP3 music media data(not the Tag frame data) start with
>>>>> "ID3", but this "ID3" is not the ID3v2 Tag's identifier.
>>>>>
>>>>> In fact the MP3 file without ID3v2 Tags, only ID3v1 exist.
>>>>>
>>>>> do you think this situation would like happen.
>>>>>
>>>>> thank u again...
>>>>>
>>>>> Jud White 写道:
>>>>>       
>>>>>           
>>>>>> An ID3v2 tag can be detected with the following pattern:
>>>>>> $49 44 33 yy yy xx zz zz zz zz
>>>>>> Where yy is less than $FF, xx is the 'flags' byte and zz is less than $80.
>>>>>>
>>>>>> http://id3.org/id3v2.3.0#head-697d09c50ed7fa96fb66c6b0a9d93585e2652b0b
>>>>>>
>>>>>>
>>>>>> hongyang wrote:
>>>>>>   
>>>>>>         
>>>>>>             
>>>>>>> Hello everyone,
>>>>>>>
>>>>>>> I have a quesetion, if I know the .mp3 file has ID3v1 Tag, and I am not
>>>>>>> sure whether it also has ID3v2 Tag.Now whether the condition would happend
>>>>>>> that the start of media data are "ID3" ,but the "ID3" is not the
>>>>>>> identifier of ID3v2.
>>>>>>>
>>>>>>> My english is very poor,so please forgave me.
>>>>>>>
>>>>>>> Thank you all.
>>>>>>>
>>>>>>> hongyang
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>>   
>>>>>>>     
>>>>>>>           
>>>>>>>               
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>>>>>>
>>>>>>
>>>>>>   
>>>>>>         
>>>>>>             
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>>>>
>>>>
>>>>
>>>>     
>>>>         
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>>>
>>>   
>>>       
>
>
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>   

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