avcodec/adpcm_ms: support custom block size for encoding

Fixes tickets #6585 and #7109

Signed-off-by: Zane van Iperen <zane@zanevaniperen.com>

libavcodec/adpcmenc.c

@@ -127,9 +127,9 @@ static av_cold int adpcm_encode_init(AVCodecContext *avctx)
     case AV_CODEC_ID_ADPCM_MS:
         /* each 16 bits sample gives one nibble
            and we have 7 bytes per channel overhead */
-        avctx->frame_size = (BLKSIZE - 7 * avctx->channels) * 2 / avctx->channels + 2;
+        avctx->frame_size = (s->block_size - 7 * avctx->channels) * 2 / avctx->channels + 2;
         avctx->bits_per_coded_sample = 4;
-        avctx->block_align    = BLKSIZE;
+        avctx->block_align     = s->block_size;
         if (!(avctx->extradata = av_malloc(32 + AV_INPUT_BUFFER_PADDING_SIZE)))
             return AVERROR(ENOMEM);
         avctx->extradata_size = 32;