[FFmpeg-devel] [PATCH 1/2] mpegts: add all stream languages into metadata

[Anssi Hannula]

On 07.03.2011 21:50, Ronald S. Bultje wrote:
> Hi,
> 
> 2011/3/7 M?ns Rullg?rd <mans at mansr.com>:
>> "Ronald S. Bultje" <rsbultje at gmail.com> writes:
>>
>>> Hi,
>>>
>>> On Thu, Feb 17, 2011 at 10:26 AM, Anssi Hannula <anssi.hannula at iki.fi> wrote:
>>>> This is used at least on some older DVB broadcasts for dual-mono audio
>>>> tracks.
>>>> ---
>>>>
>>>> Here goes the patchset without the channelX/language stuff.
>>>> I also changed the language separator from '+' from ',', but I'm open
>>>> to bikeshedding.
>>>>
>>>>  libavformat/mpegts.c |   18 ++++++++++++------
>>>>  1 files changed, 12 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
>>>> index abb6f08..c7e4fe3 100644
>>>> --- a/libavformat/mpegts.c
>>>> +++ b/libavformat/mpegts.c
>>>> @@ -890,7 +890,8 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
>>>>  {
>>>>     const uint8_t *desc_end;
>>>>     int desc_len, desc_tag;
>>>> -    char language[4];
>>>> +    char language[252];
>>>> +    int i;
>>>>
>>>>     desc_tag = get8(pp, desc_list_end);
>>>>     if (desc_tag < 0)
>>>> @@ -949,16 +950,21 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
>>>>         av_metadata_set2(&st->metadata, "language", language, 0);
>>>>         break;
>>>>     case 0x0a: /* ISO 639 language descriptor */
>>>> -        language[0] = get8(pp, desc_end);
>>>> -        language[1] = get8(pp, desc_end);
>>>> -        language[2] = get8(pp, desc_end);
>>>> -        language[3] = 0;
>>>> -        av_metadata_set2(&st->metadata, "language", language, 0);
>>>> +        for (i = 0; i + 4 <= desc_len; i += 4) {
>>>> +            language[i + 0] = get8(pp, desc_end);
>>>> +            language[i + 1] = get8(pp, desc_end);
>>>> +            language[i + 2] = get8(pp, desc_end);
>>>> +            language[i + 3] = ',';
>>>>         switch (get8(pp, desc_end)) {
>>>>             case 0x01: st->disposition |= AV_DISPOSITION_CLEAN_EFFECTS; break;
>>>>             case 0x02: st->disposition |= AV_DISPOSITION_HEARING_IMPAIRED; break;
>>>>             case 0x03: st->disposition |= AV_DISPOSITION_VISUAL_IMPAIRED; break;
>>>>         }
>>>> +        }
>>>> +        if (i) {
>>>> +            language[i - 1] = 0;
>>>> +            av_metadata_set2(&st->metadata, "language", language, 0);
>>>> +        }
>>>
>>> if language[] is 252 bytes, can this overflow? There's no checks for i
>>> being under 252.
>>
>> desc_len is an 8-bit field in the stream.
> 
> So shouldn't language[] be 256 bytes at least then?

Maximum value of a 8-bit field is 255, and in 255 bytes there can only
be 63 4-byte tags, which means 63 three-letter codes plus commas plus
null byte, 63*3 + 62 + 1 = 252.

-- 
Anssi Hannula