Re: [FFmpeg-devel] [PATCH 1/3] avformat/mp3dec: only call ffio_ensure_seekback once

[Marton Balint <cus@passwd.hu>]

On Tue, 14 May 2024, Marton Balint wrote:

> Otherwise the subsequent ffio_ensure_seekback calls destroy the buffer of the
> earlier. The worst case ~66kB seekback is so small it is easier to request it
> entirely.
>
> Fixes ticket #10837, a regression since
> 0d17f5228f4d3854066ec1001f69c7d1714b0df9.

Will apply the series in 1-2 days.

Regards,
Marton

>
> Signed-off-by: Marton Balint <cus@passwd.hu>
> ---
> libavformat/mp3dec.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c
> index ec6cf567bc..78d6c8c71c 100644
> --- a/libavformat/mp3dec.c
> +++ b/libavformat/mp3dec.c
> @@ -32,6 +32,7 @@
> #include "replaygain.h"
>
> #include "libavcodec/codec_id.h"
> +#include "libavcodec/mpegaudio.h"
> #include "libavcodec/mpegaudiodecheader.h"
>
> #define XING_FLAG_FRAMES 0x01
> @@ -400,15 +401,16 @@ static int mp3_read_header(AVFormatContext *s)
>     if (ret < 0)
>         return ret;
>
> +    ret = ffio_ensure_seekback(s->pb, 64 * 1024 + MPA_MAX_CODED_FRAME_SIZE + 4);
> +    if (ret < 0)
> +        return ret;
> +
>     off = avio_tell(s->pb);
>     for (i = 0; i < 64 * 1024; i++) {
>         uint32_t header, header2;
>         int frame_size;
> -        if (!(i&1023))
> -            ffio_ensure_seekback(s->pb, i + 1024 + 4);
>         frame_size = check(s->pb, off + i, &header);
>         if (frame_size > 0) {
> -            ffio_ensure_seekback(s->pb, i + 1024 + frame_size + 4);
>             ret = check(s->pb, off + i + frame_size, &header2);
>             if (ret >= 0 &&
>                 (header & MP3_MASK) == (header2 & MP3_MASK))
> -- 
> 2.35.3
>
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