avcodec/adpcm_ima_amv: document header format

Zane van Iperen committed 6 years ago

Commit 8903cb31 parent 50d3a751 file · +10 −0Browse files

Unified · Split

libavcodec/adpcm.c+10−0

@@ -1690,6 +1690,16 @@ static int adpcm_decode_frame(AVCodecContext avctx, void data, · 1689 unmodified lines
1690	1690	case AV_CODEC_ID_ADPCM_IMA_AMV:
1691	1691	av_assert0(avctx->channels == 1);
1692	1692
	1693	+ /*
	1694	+ * Header format:
	1695	+ * int16_t predictor;
	1696	+ * uint8_t step_index;
	1697	+ * uint8_t reserved;
	1698	+ * uint32_t frame_size;
	1699	+ *
	1700	+ * Some implementations have step_index as 16-bits, but others
	1701	+ * only use the lower 8 and store garbage in the upper 8.
	1702	+ */
1693	1703	c->status[0].predictor = sign_extend(bytestream2_get_le16u(&gb), 16);
1694	1704	c->status[0].step_index = bytestream2_get_byteu(&gb);
1695	1705	bytestream2_skipu(&gb, 5);