From 8903cb3c15344d90a6959cd5f416b74e4ef23dbc Mon Sep 17 00:00:00 2001 From: Zane van Iperen Date: Mon, 2 Nov 2020 15:47:26 +1000 Subject: [PATCH] avcodec/adpcm_ima_amv: document header format Signed-off-by: Zane van Iperen --- libavcodec/adpcm.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/libavcodec/adpcm.c b/libavcodec/adpcm.c index 7762694e3e..01aced2e10 100644 --- a/libavcodec/adpcm.c +++ b/libavcodec/adpcm.c @@ -1690,6 +1690,16 @@ static int adpcm_decode_frame(AVCodecContext *avctx, void *data, case AV_CODEC_ID_ADPCM_IMA_AMV: av_assert0(avctx->channels == 1); + /* + * Header format: + * int16_t predictor; + * uint8_t step_index; + * uint8_t reserved; + * uint32_t frame_size; + * + * Some implementations have step_index as 16-bits, but others + * only use the lower 8 and store garbage in the upper 8. + */ c->status[0].predictor = sign_extend(bytestream2_get_le16u(&gb), 16); c->status[0].step_index = bytestream2_get_byteu(&gb); bytestream2_skipu(&gb, 5);