[FFmpeg-devel] Re: [PATCH] avcodec/adpcm: Fix the decoding error caused by incorrect retrieval of step_index in ADPCM module

[James Almer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

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>>From 3a21c9f12121f3e8bcaa704422750a8f45c7e50e Mon Sep 17 00:00:00 2001
> From: tangsha <tangsha@kylinos.cn>
> Date: Thu, 28 Aug 2025 17:45:19 +0800
> Subject: [PATCH] avcodec/adpcm: Fix the decoding error caused by incorrect
>  retrieval of step_index in ADPCM module
> 
> ---
>  libavcodec/adpcm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c
> index 4c15be6207..d01d6cd8e4 100644
> --- a/libavcodec/adpcm.c
> +++ b/libavcodec/adpcm.c
> @@ -1345,7 +1345,8 @@ static int adpcm_decode_frame(AVCodecContext *avctx, AVFrame *frame,

Those line offsets are not from the master branch. Are you writing this 
targeting a release branch?

>              ADPCMChannelStatus *cs = &c->status[i];
>              cs->predictor = samples_p[i][0] = sign_extend(bytestream2_get_le16u(&gb), 16);
>  
> -            cs->step_index = sign_extend(bytestream2_get_le16u(&gb), 16);
> +            cs->step_index = bytestream2_get_byteu(&gb);
> +            bytestream2_skip(&gb, sizeof(uint8_t));

What's in this byte if not a part of step_index? Also, do you have a 
sample that gets fixed by this change?

>              if (cs->step_index > 88u){
>                  av_log(avctx, AV_LOG_ERROR, "ERROR: step_index[%d] = %i\n",
>                         i, cs->step_index);
> -- 
> 2.25.1
> 

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