[FFmpeg-devel] Stack usage in FFmpeg

[Baptiste Coudurier]

On 11/20/2009 01:57 PM, Reimar D?ffinger wrote:
> On Sun, Nov 01, 2009 at 08:50:15PM +0000, M?ns Rullg?rd wrote:
>>    61440 mxf_get_d10_aes3_packet        mxfdec.c:216
>
> This seems really silly,

Please spare the useless comment.

> unless I miss something this could just be done in-place...

Seems so.

> (of course I assume that the load-store mismatches are not going to
> break performance in any relevant way).
> Patch to get rid of the stack usage:
> Index: libavformat/mxfdec.c
> ===================================================================
> --- libavformat/mxfdec.c	(revision 20562)
> +++ libavformat/mxfdec.c	(working copy)
> @@ -214,18 +214,17 @@
>   /* XXX: use AVBitStreamFilter */
>   static int mxf_get_d10_aes3_packet(ByteIOContext *pb, AVStream *st, AVPacket *pkt, int64_t length)
>   {
> -    uint8_t buffer[61444];
>       const uint8_t *buf_ptr, *end_ptr;
>       uint8_t *data_ptr;
>       int i;
>
>       if (length>  61444) /* worst case PAL 1920 samples 8 channels */
>           return -1;
> -    get_buffer(pb, buffer, length);
>       av_new_packet(pkt, length);
> +    get_buffer(pb, pkt->data, length);
>       data_ptr = pkt->data;
> -    end_ptr = buffer + length;
> -    buf_ptr = buffer + 4; /* skip SMPTE 331M header */
> +    end_ptr = pkt->data + length;
> +    buf_ptr = pkt->data + 4; /* skip SMPTE 331M header */
>       for (; buf_ptr<  end_ptr; ) {
>           for (i = 0; i<  st->codec->channels; i++) {
>               uint32_t sample = bytestream_get_le32(&buf_ptr);

Should be ok if it works.

-- 
Baptiste COUDURIER
Key fingerprint                 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
FFmpeg maintainer                                  http://www.ffmpeg.org