Re: [FFmpeg-devel] [PATCH 06/13] avcodec/mpegvideo_enc: Don't overallocate arrays

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Andreas Rheinhardt:
> Michael Niedermayer:
>> On Fri, Oct 06, 2023 at 04:46:29AM +0200, Andreas Rheinhardt wrote:
>>> Only entries 0..max_b_frames are ever used.
>>>
>>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
>>> ---
>>>  libavcodec/mpegvideo_enc.c | 10 +++++-----
>>>  1 file changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/libavcodec/mpegvideo_enc.c b/libavcodec/mpegvideo_enc.c
>>> index 1e0aed8db9..c06fdd08fe 100644
>>> --- a/libavcodec/mpegvideo_enc.c
>>> +++ b/libavcodec/mpegvideo_enc.c
>>> @@ -819,8 +819,8 @@ av_cold int ff_mpv_encode_init(AVCodecContext *avctx)
>>>          !FF_ALLOCZ_TYPED_ARRAY(s->q_intra_matrix16,        32) ||
>>>          !FF_ALLOCZ_TYPED_ARRAY(s->q_chroma_intra_matrix16, 32) ||
>>>          !FF_ALLOCZ_TYPED_ARRAY(s->q_inter_matrix16,        32) ||
>>> -        !FF_ALLOCZ_TYPED_ARRAY(s->input_picture,           MAX_PICTURE_COUNT) ||
>>> -        !FF_ALLOCZ_TYPED_ARRAY(s->reordered_input_picture, MAX_PICTURE_COUNT))
>>> +        !FF_ALLOCZ_TYPED_ARRAY(s->input_picture,           MAX_B_FRAMES + 1) ||
>>> +        !FF_ALLOCZ_TYPED_ARRAY(s->reordered_input_picture, MAX_B_FRAMES + 1))
>>>          return AVERROR(ENOMEM);
>>>  
>>>      /* Allocate MV tables; the MV and MB tables will be copied
>>> @@ -1231,7 +1231,7 @@ static int load_input_picture(MpegEncContext *s, const AVFrame *pic_arg)
>>>      }
>>>  
>>>      /* shift buffer entries */
>>> -    for (i = flush_offset; i < MAX_PICTURE_COUNT /*s->encoding_delay + 1*/; i++)
>>> +    for (int i = flush_offset; i <= MAX_B_FRAMES; i++)
>>>          s->input_picture[i - flush_offset] = s->input_picture[i];
>>>  
>>>      s->input_picture[encoding_delay] = pic;
>>> @@ -1450,9 +1450,9 @@ static int select_input_picture(MpegEncContext *s)
>>>  {
>>>      int i, ret;
>>>  
>>> -    for (i = 1; i < MAX_PICTURE_COUNT; i++)
>>> +    for (int i = 1; i <= MAX_B_FRAMES; i++)
>>>          s->reordered_input_picture[i - 1] = s->reordered_input_picture[i];
>>
>> I see the addition of "int" and that seems neither needed nor
>> explained why in the commit message
>>
> 
> It's part of the general switch to the loop-based iterators wherever
> possible (it is better because it automatically indicates that the value
> at the end of the loop doesn't matter and it also allows to more easily
> move blocks of code around). I always use them when I touch a loop.
> 
> If it matters: That i in the outer scope survives this patchset, but it
> won't survive for long.
> 

Are you ok with this patch and the rest of the patchset? I'd like to
apply it tomorrow unless there are objections.

- Andreas

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