Fix dont and doesnt typos

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/frame_thread_encoder.c

@@ -142,7 +142,7 @@ int ff_frame_thread_encoder_init(AVCodecContext *avctx, AVDictionary *options){
 
     if (avctx->codec_id == AV_CODEC_ID_HUFFYUV ||
         avctx->codec_id == AV_CODEC_ID_FFVHUFF) {
-        // huffyuv doesnt support these with multiple frame threads currently
+        // huffyuv does not support these with multiple frame threads currently
         if (avctx->context_model > 0 || (avctx->flags & CODEC_FLAG_PASS1)) {
             av_log(avctx, AV_LOG_WARNING,
                "Forcing thread count to 1 for huffyuv encoding with first pass or context 1\n");

libavformat/avidec.c

@@ -438,7 +438,7 @@ static int calculate_bitrate(AVFormatContext *s)
         maxpos = FFMAX(maxpos, st->index_entries[j-1].pos);
         lensum += len;
     }
-    if (maxpos < avi->io_fsize*9/10) // index doesnt cover the whole file
+    if (maxpos < avi->io_fsize*9/10) // index does not cover the whole file
         return 0;
     if (lensum*9/10 > maxpos || lensum < maxpos*9/10) // frame sum and filesize mismatch
         return 0;

libavformat/oggdec.c

@@ -837,7 +837,7 @@ static int64_t ogg_read_timestamp(AVFormatContext *s, int stream_index,
            && !ogg_packet(s, &i, &pstart, &psize, pos_arg)) {
         if (i == stream_index) {
             struct ogg_stream *os = ogg->streams + stream_index;
-            // Dont trust the last timestamps of a ogm video
+            // Do not trust the last timestamps of a ogm video
             if (    (os->flags & OGG_FLAG_EOS)
                 && !(os->flags & OGG_FLAG_BOS)
                 && os->codec == &ff_ogm_video_codec)