Re: [FFmpeg-devel] [PATCH] cbs_mpeg2_split_fragment(): cache the buffer end

[Scott Theisen <scott.the.elm@gmail.com>]

Ping; it still applies cleanly.

-Scott Theisen

On 5/15/22 14:50, Scott Theisen wrote:
> Ping; it still applies cleanly.
>
> -Scott Theisen
>
> On 2/8/22 15:32, Scott Theisen wrote:
>> Also add a few clarifying comments.
>> ---
>>   libavcodec/cbs_mpeg2.c | 16 ++++++++--------
>>   1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c
>> index 33bd3e0998..47732562d1 100644
>> --- a/libavcodec/cbs_mpeg2.c
>> +++ b/libavcodec/cbs_mpeg2.c
>> @@ -144,12 +144,12 @@ static int 
>> cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
>>                                       CodedBitstreamFragment *frag,
>>                                       int header)
>>   {
>> -    const uint8_t *start;
>> +    const uint8_t *start = frag->data;
>> +    const uint8_t * const buf_end = frag->data + frag->data_size;
>>       uint32_t start_code = -1;
>>       int err;
>>   -    start = avpriv_find_start_code(frag->data, frag->data + 
>> frag->data_size,
>> -                                   &start_code);
>> +    start = avpriv_find_start_code(start, buf_end, &start_code);
>>       if (start_code >> 8 != 0x000001) {
>>           // No start code found.
>>           return AVERROR_INVALIDDATA;
>> @@ -165,12 +165,11 @@ static int 
>> cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
>>           // start code in any way (as e.g. happens when there is a
>>           // Sequence End unit at the very end of a packet).
>>           start_code = UINT32_MAX;
>> -        end = avpriv_find_start_code(start--, frag->data + 
>> frag->data_size,
>> -                                     &start_code);
>> -
>> -        // start points to the byte containing the 
>> start_code_identifier
>> +        end = avpriv_find_start_code(start, buf_end, &start_code);
>> +        start--;
>> +        // decrement so start points to the byte containing the 
>> start_code_identifier
>>           // (may be the last byte of fragment->data); end points to 
>> the byte
>> -        // following the byte containing the start code identifier 
>> (or to
>> +        // following the byte containing the next start code 
>> identifier (or to
>>           // the end of fragment->data).
>>           if (start_code >> 8 == 0x000001) {
>>               // Unit runs from start to the beginning of the start code
>> @@ -178,6 +177,7 @@ static int 
>> cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
>>               unit_size = (end - 4) - start;
>>           } else {
>>              // We didn't find a start code, so this is the final unit.
>> +           // There is no start code to remove from end, hence not 
>> (end - 4).
>>              unit_size = end - start;
>>           }
>

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