[Ffmpeg-devel] [PATCH] Read AVI tags

[David Conrad]

Hi,

On Aug 16, 2006, at 4:40 AM, Michael Niedermayer wrote:
> Hi
>
> On Tue, Aug 15, 2006 at 03:25:07PM -0400, David Conrad wrote:
>> On Aug 15, 2006, at 4:00 AM, Benjamin Larsson wrote:
>>
>>> Hi,
>>>
>>> David Conrad skrev:
>>>> On Aug 15, 2006, at 1:39 AM, David Conrad wrote:
>>>>
>>>>> Hi,
>>>>> The following patch adds some read support for metadata tags in
>>>>> AVI files. One note: the artist tag is put in the author field
>>>>> since there is no AVI tag for author, but this seems to be the
>>>>> same behavior as the mp3 parser's id3 tag reader.
>>>>
>>>> My apologies, please ignore that last patch. The correct one  
>>>> follows.
>>>>
>>>> -David
>>>>
>>>
>>> can you implement writing also ? You can look here for a patch
>>> noone cleaned up enough to commit. http://thread.gmane.org/
>>> gmane.comp.video.ffmpeg.devel/28596/focus=28596
>>
>> Okay, I cleaned up that patch for writing, and I think I addressed
>> all of your and Micheal's concerns with the original. One thing,
>> though, is that the hash for the two test AVI files for ffserver
>> changed for me; the original patch doesn't indicate this.
>>
>> -David
>
>> Index: libavformat/avienc.c
>> ===================================================================
>> --- libavformat/avienc.c	(revision 5999)
>> +++ libavformat/avienc.c	(working copy)
>> @@ -89,6 +89,19 @@
>>      return tag;
>>  }
>>
>> +static void avi_write_info_tag(ByteIOContext *pb, const char  
>> *tag, const char *contents)
>> +{
>> +    int len = strlen(contents);
>> +    if (len > 0) {
>> +        len++;
>> +        put_tag(pb, tag);
>> +        put_le32(pb, len);
>> +        put_buffer(pb, contents, len);
>> +        if (len & 1)
>> +            put_byte(pb, 0);
>> +    }
>> +}
>
> this could use put_strz()
>
>
> [...]
>> +    avi_write_info_tag(pb, "ISFT", "libavformat " AV_STRINGIFY 
>> (LIBAVFORMAT_VERSION));
>
> this should be under CODEC_FLAG_BITEXACT check so regression tests  
> dont break
> if the version changes
>
>
>> +    end_tag(pb, list2);
>> +    list2 = start_tag(pb, "JUNK");
>> +    for (i = 0; i < 1016; i += 4)
>> +        put_le32(pb, 0);
>> +    end_tag(pb, list2);
>
> what is that good for?

It provides expansion space for editing tags without the need to  
rewrite the entire file. Most muxers give between one and two  
kilobytes for this.

How does this version look?

-David
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