From d28250eada1b4c257d6810b83129e18e5346e4ed Mon Sep 17 00:00:00 2001 From: tangsha Date: Mon, 1 Dec 2025 16:15:35 +0800 Subject: [PATCH] avcodec/adpcm: Fix step_index decoding by skipping padding byte The bug was caused by incorrect reading of the step_index field: the original code read a 16-bit value (including a padding byte) instead of the correct 8-bit step_index as defined by the ADPCM format. This led to distorted audio or incorrect step calculations when decoding specific ADPCM-encoded files. Fix by: 1. Reading step_index as an 8-bit unsigned byte via bytestream2_get_byteu() 2. Skipping the subsequent 8-bit padding byte with bytestream2_skip() --- libavcodec/adpcm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c index 3da0791ba3..31340af677 100644 --- a/libavcodec/adpcm.c +++ b/libavcodec/adpcm.c @@ -1512,7 +1512,8 @@ static int adpcm_decode_frame(AVCodecContext *avctx, AVFrame *frame, 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_skipu(&gb, 1); if (cs->step_index > 88u){ av_log(avctx, AV_LOG_ERROR, "ERROR: step_index[%d] = %i\n", i, cs->step_index);