diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c
index b9762be9c9..eee7978452 100644
--- a/libavcodec/h263dec.c
+++ b/libavcodec/h263dec.c
@@ -113,23 +113,23 @@ av_cold int ff_h263_decode_init(AVCodecContext *avctx)
         break;
     case AV_CODEC_ID_MSMPEG4V1:
         s->h263_pred       = 1;
-        s->msmpeg4_version = 1;
+        s->msmpeg4_version = MSMP4_V1;
         break;
     case AV_CODEC_ID_MSMPEG4V2:
         s->h263_pred       = 1;
-        s->msmpeg4_version = 2;
+        s->msmpeg4_version = MSMP4_V2;
         break;
     case AV_CODEC_ID_MSMPEG4V3:
         s->h263_pred       = 1;
-        s->msmpeg4_version = 3;
+        s->msmpeg4_version = MSMP4_V3;
         break;
     case AV_CODEC_ID_WMV1:
         s->h263_pred       = 1;
-        s->msmpeg4_version = 4;
+        s->msmpeg4_version = MSMP4_WMV1;
         break;
     case AV_CODEC_ID_WMV2:
         s->h263_pred       = 1;
-        s->msmpeg4_version = 5;
+        s->msmpeg4_version = MSMP4_WMV2;
         break;
     case AV_CODEC_ID_H263I:
         break;
@@ -227,7 +227,7 @@ static int decode_slice(MpegEncContext *s)
 
     for (; s->mb_y < s->mb_height; s->mb_y++) {
         /* per-row end of slice checks */
-        if (s->msmpeg4_version) {
+        if (s->msmpeg4_version != MSMP4_UNUSED) {
             if (s->resync_mb_y + s->slice_height == s->mb_y) {
                 ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                                 s->mb_x - 1, s->mb_y, ER_MB_END);
@@ -236,7 +236,7 @@ static int decode_slice(MpegEncContext *s)
             }
         }
 
-        if (s->msmpeg4_version == 1) {
+        if (s->msmpeg4_version == MSMP4_V1) {
             s->last_dc[0] =
             s->last_dc[1] =
             s->last_dc[2] = 128;
@@ -375,12 +375,12 @@ static int decode_slice(MpegEncContext *s)
     }
 
     // handle formats which don't have unique end markers
-    if (s->msmpeg4_version || (s->workaround_bugs & FF_BUG_NO_PADDING)) { // FIXME perhaps solve this more cleanly
+    if (s->msmpeg4_version != MSMP4_UNUSED || (s->workaround_bugs & FF_BUG_NO_PADDING)) { // FIXME perhaps solve this more cleanly
         int left      = get_bits_left(&s->gb);
         int max_extra = 7;
 
         /* no markers in M$ crap */
-        if (s->msmpeg4_version && s->pict_type == AV_PICTURE_TYPE_I)
+        if (s->msmpeg4_version != MSMP4_UNUSED && s->pict_type == AV_PICTURE_TYPE_I)
             max_extra += 17;
 
         /* buggy padding but the frame should still end approximately at
@@ -474,10 +474,12 @@ retry:
         return ret;
 
     /* let's go :-) */
-    if (CONFIG_WMV2_DECODER && s->msmpeg4_version == 5) {
+    if (CONFIG_WMV2_DECODER && s->msmpeg4_version == MSMP4_WMV2) {
         ret = ff_wmv2_decode_picture_header(s);
-    } else if (CONFIG_MSMPEG4DEC && s->msmpeg4_version) {
+#if CONFIG_MSMPEG4DEC
+    } else if (s->msmpeg4_version != MSMP4_UNUSED) {
         ret = ff_msmpeg4_decode_picture_header(s);
+#endif
     } else if (CONFIG_MPEG4_DECODER && avctx->codec_id == AV_CODEC_ID_MPEG4) {
         ret = ff_mpeg4_decode_picture_header(avctx->priv_data, &s->gb, 0, 0);
         s->skipped_last_frame = (ret == FRAME_SKIPPED);
@@ -583,13 +585,15 @@ retry:
     /* the second part of the wmv2 header contains the MB skip bits which
      * are stored in current_picture->mb_type which is not available before
      * ff_mpv_frame_start() */
-    if (CONFIG_WMV2_DECODER && s->msmpeg4_version == 5) {
+#if CONFIG_WMV2_DECODER
+    if (s->msmpeg4_version == MSMP4_WMV2) {
         ret = ff_wmv2_decode_secondary_picture_header(s);
         if (ret < 0)
             return ret;
         if (ret == 1)
             goto frame_end;
     }
+#endif
 
     /* decode each macroblock */
     s->mb_x = 0;
@@ -597,7 +601,7 @@ retry:
 
     slice_ret = decode_slice(s);
     while (s->mb_y < s->mb_height) {
-        if (s->msmpeg4_version) {
+        if (s->msmpeg4_version != MSMP4_UNUSED) {
             if (s->slice_height == 0 || s->mb_x != 0 || slice_ret < 0 ||
                 (s->mb_y % s->slice_height) != 0 || get_bits_left(&s->gb) < 0)
                 break;
@@ -609,14 +613,14 @@ retry:
                 s->er.error_occurred = 1;
         }
 
-        if (s->msmpeg4_version < 4 && s->h263_pred)
+        if (s->msmpeg4_version < MSMP4_WMV1 && s->h263_pred)
             ff_mpeg4_clean_buffers(s);
 
         if (decode_slice(s) < 0)
             slice_ret = AVERROR_INVALIDDATA;
     }
 
-    if (s->msmpeg4_version && s->msmpeg4_version < 4 &&
+    if (s->msmpeg4_version != MSMP4_UNUSED && s->msmpeg4_version < MSMP4_WMV1 &&
         s->pict_type == AV_PICTURE_TYPE_I)
         if (!CONFIG_MSMPEG4DEC ||
             ff_msmpeg4_decode_ext_header(s, buf_size) < 0)
diff --git a/libavcodec/motion_est.c b/libavcodec/motion_est.c
index 892e2a3d08..cab66bff0c 100644
--- a/libavcodec/motion_est.c
+++ b/libavcodec/motion_est.c
@@ -1608,7 +1608,7 @@ int ff_get_best_fcode(MpegEncContext * s, const int16_t (*mv_table)[2], int type
         int best_fcode=-1;
         int best_score=-10000000;
 
-        if(s->msmpeg4_version)
+        if (s->msmpeg4_version != MSMP4_UNUSED)
             range= FFMIN(range, 16);
         else if(s->codec_id == AV_CODEC_ID_MPEG2VIDEO && s->avctx->strict_std_compliance >= FF_COMPLIANCE_NORMAL)
             range= FFMIN(range, 256);
@@ -1659,9 +1659,9 @@ void ff_fix_long_p_mvs(MpegEncContext * s, int type)
     int y, range;
     av_assert0(s->pict_type==AV_PICTURE_TYPE_P);
 
-    range = (((s->out_format == FMT_MPEG1 || s->msmpeg4_version) ? 8 : 16) << f_code);
+    range = (((s->out_format == FMT_MPEG1 || s->msmpeg4_version != MSMP4_UNUSED) ? 8 : 16) << f_code);
 
-    av_assert0(range <= 16 || !s->msmpeg4_version);
+    av_assert0(range <= 16 || s->msmpeg4_version == MSMP4_UNUSED);
     av_assert0(range <=256 || !(s->codec_id == AV_CODEC_ID_MPEG2VIDEO && s->avctx->strict_std_compliance >= FF_COMPLIANCE_NORMAL));
 
     if(c->avctx->me_range && range > c->avctx->me_range) range= c->avctx->me_range;
@@ -1708,7 +1708,7 @@ void ff_fix_long_mvs(MpegEncContext * s, uint8_t *field_select_table, int field_
     int y, h_range, v_range;
 
     // RAL: 8 in MPEG-1, 16 in MPEG-4
-    int range = (((s->out_format == FMT_MPEG1 || s->msmpeg4_version) ? 8 : 16) << f_code);
+    int range = (((s->out_format == FMT_MPEG1 || s->msmpeg4_version != MSMP4_UNUSED) ? 8 : 16) << f_code);
 
     if(c->avctx->me_range && range > c->avctx->me_range) range= c->avctx->me_range;
 
diff --git a/libavcodec/mpegvideo.c b/libavcodec/mpegvideo.c
index 3cb8d06914..ec0f2d5bed 100644
--- a/libavcodec/mpegvideo.c
+++ b/libavcodec/mpegvideo.c
@@ -381,7 +381,7 @@ static int init_duplicate_context(MpegEncContext *s)
     s->block = s->blocks[0];
 
     if (s->out_format == FMT_H263) {
-        int mb_height = s->msmpeg4_version == 6 /* VC-1 like */ ?
+        int mb_height = s->msmpeg4_version == MSMP4_VC1 ?
                             FFALIGN(s->mb_height, 2) : s->mb_height;
         int y_size = s->b8_stride * (2 * mb_height + 1);
         int c_size = s->mb_stride * (mb_height + 1);
@@ -535,7 +535,7 @@ int ff_mpv_init_context_frame(MpegEncContext *s)
     /* VC-1 can change from being progressive to interlaced on a per-frame
      * basis. We therefore allocate certain buffers so big that they work
      * in both instances. */
-    mb_height = s->msmpeg4_version == 6 /* VC-1 like*/ ?
+    mb_height = s->msmpeg4_version == MSMP4_VC1 ?
                     FFALIGN(s->mb_height, 2) : s->mb_height;
 
     s->mb_width   = (s->width + 15) / 16;
@@ -592,7 +592,7 @@ int ff_mpv_init_context_frame(MpegEncContext *s)
         }
     }
 
-    if (s->msmpeg4_version >= 3) {
+    if (s->msmpeg4_version >= MSMP4_V3) {
         s->coded_block_base = av_mallocz(y_size);
         if (!s->coded_block_base)
             return AVERROR(ENOMEM);
diff --git a/libavcodec/mpegvideo.h b/libavcodec/mpegvideo.h
index 43d28a269a..70b9a55450 100644
--- a/libavcodec/mpegvideo.h
+++ b/libavcodec/mpegvideo.h
@@ -419,7 +419,15 @@ typedef struct MpegEncContext {
     int slice_height;      ///< in macroblocks
     int first_slice_line;  ///< used in MPEG-4 too to handle resync markers
     int flipflop_rounding;
-    int msmpeg4_version;   ///< 0=not msmpeg4, 1=mp41, 2=mp42, 3=mp43/divx3 4=wmv1/7 5=wmv2/8
+    enum {
+        MSMP4_UNUSED,
+        MSMP4_V1,
+        MSMP4_V2,
+        MSMP4_V3,
+        MSMP4_WMV1,
+        MSMP4_WMV2,
+        MSMP4_VC1,        ///< for VC1 (image), WMV3 (image) and MSS2.
+    } msmpeg4_version;
     int per_mb_rl_table;
     int esc3_level_length;
     int esc3_run_length;
diff --git a/libavcodec/mpegvideo_enc.c b/libavcodec/mpegvideo_enc.c
index ddd68f2da8..a59b414d88 100644
--- a/libavcodec/mpegvideo_enc.c
+++ b/libavcodec/mpegvideo_enc.c
@@ -754,7 +754,7 @@ av_cold int ff_mpv_encode_init(AVCodecContext *avctx)
         s->out_format      = FMT_H263;
         s->h263_pred       = 1;
         s->unrestricted_mv = 1;
-        s->msmpeg4_version = 2;
+        s->msmpeg4_version = MSMP4_V2;
         avctx->delay       = 0;
         s->low_delay       = 1;
         break;
@@ -762,7 +762,7 @@ av_cold int ff_mpv_encode_init(AVCodecContext *avctx)
         s->out_format        = FMT_H263;
         s->h263_pred         = 1;
         s->unrestricted_mv   = 1;
-        s->msmpeg4_version   = 3;
+        s->msmpeg4_version   = MSMP4_V3;
         s->flipflop_rounding = 1;
         avctx->delay         = 0;
         s->low_delay         = 1;
@@ -771,7 +771,7 @@ av_cold int ff_mpv_encode_init(AVCodecContext *avctx)
         s->out_format        = FMT_H263;
         s->h263_pred         = 1;
         s->unrestricted_mv   = 1;
-        s->msmpeg4_version   = 4;
+        s->msmpeg4_version   = MSMP4_WMV1;
         s->flipflop_rounding = 1;
         avctx->delay         = 0;
         s->low_delay         = 1;
@@ -780,7 +780,7 @@ av_cold int ff_mpv_encode_init(AVCodecContext *avctx)
         s->out_format        = FMT_H263;
         s->h263_pred         = 1;
         s->unrestricted_mv   = 1;
-        s->msmpeg4_version   = 5;
+        s->msmpeg4_version   = MSMP4_WMV2;
         s->flipflop_rounding = 1;
         avctx->delay         = 0;
         s->low_delay         = 1;
@@ -916,8 +916,10 @@ av_cold int ff_mpv_encode_init(AVCodecContext *avctx)
 
     if (CONFIG_H263_ENCODER && s->out_format == FMT_H263) {
         ff_h263_encode_init(s);
-        if (CONFIG_MSMPEG4ENC && s->msmpeg4_version)
+#if CONFIG_MSMPEG4ENC
+        if (s->msmpeg4_version != MSMP4_UNUSED)
             ff_msmpeg4_encode_init(s);
+#endif
     }
 
     /* init q matrix */
@@ -3459,9 +3461,12 @@ static int encode_thread(AVCodecContext *c, void *arg){
         }
     }
 
+#if CONFIG_MSMPEG4ENC
     //not beautiful here but we must write it before flushing so it has to be here
-    if (CONFIG_MSMPEG4ENC && s->msmpeg4_version && s->msmpeg4_version<4 && s->pict_type == AV_PICTURE_TYPE_I)
+    if (s->msmpeg4_version != MSMP4_UNUSED && s->msmpeg4_version < MSMP4_WMV1 &&
+        s->pict_type == AV_PICTURE_TYPE_I)
         ff_msmpeg4_encode_ext_header(s);
+#endif
 
     write_slice_end(s);
 
@@ -3565,7 +3570,7 @@ static int encode_picture(MpegEncContext *s, const AVPacket *pkt)
 
     /* we need to initialize some time vars before we can encode B-frames */
     // RAL: Condition added for MPEG1VIDEO
-    if (s->out_format == FMT_MPEG1 || (s->h263_pred && !s->msmpeg4_version))
+    if (s->out_format == FMT_MPEG1 || (s->h263_pred && s->msmpeg4_version == MSMP4_UNUSED))
         set_frame_distances(s);
     if(CONFIG_MPEG4_ENCODER && s->codec_id == AV_CODEC_ID_MPEG4)
         ff_set_mpeg4_time(s);
@@ -3575,8 +3580,7 @@ static int encode_picture(MpegEncContext *s, const AVPacket *pkt)
 //    s->lambda= s->cur_pic.ptr->quality; //FIXME qscale / ... stuff for ME rate distortion
 
     if(s->pict_type==AV_PICTURE_TYPE_I){
-        if(s->msmpeg4_version >= 3) s->no_rounding=1;
-        else                        s->no_rounding=0;
+        s->no_rounding = s->msmpeg4_version >= MSMP4_V3;
     }else if(s->pict_type!=AV_PICTURE_TYPE_B){
         if(s->flipflop_rounding || s->codec_id == AV_CODEC_ID_H263P || s->codec_id == AV_CODEC_ID_MPEG4)
             s->no_rounding ^= 1;
@@ -3658,7 +3662,7 @@ static int encode_picture(MpegEncContext *s, const AVPacket *pkt)
         s->pict_type= AV_PICTURE_TYPE_I;
         for(i=0; i<s->mb_stride*s->mb_height; i++)
             s->mb_type[i]= CANDIDATE_MB_TYPE_INTRA;
-        if(s->msmpeg4_version >= 3)
+        if (s->msmpeg4_version >= MSMP4_V3)
             s->no_rounding=1;
         ff_dlog(s, "Scene change detected, encoding as I Frame %"PRId64" %"PRId64"\n",
                 s->mb_var_sum, s->mc_mb_var_sum);
@@ -3802,8 +3806,10 @@ static int encode_picture(MpegEncContext *s, const AVPacket *pkt)
     case FMT_H263:
         if (CONFIG_WMV2_ENCODER && s->codec_id == AV_CODEC_ID_WMV2)
             ff_wmv2_encode_picture_header(s);
-        else if (CONFIG_MSMPEG4ENC && s->msmpeg4_version)
+#if CONFIG_MSMPEG4ENC
+        else if (s->msmpeg4_version != MSMP4_UNUSED)
             ff_msmpeg4_encode_picture_header(s);
+#endif
         else if (CONFIG_MPEG4_ENCODER && s->h263_pred) {
             ret = ff_mpeg4_encode_picture_header(s);
             if (ret < 0)
diff --git a/libavcodec/mpv_reconstruct_mb_template.c b/libavcodec/mpv_reconstruct_mb_template.c
index 502e66faea..edabf2a8b4 100644
--- a/libavcodec/mpv_reconstruct_mb_template.c
+++ b/libavcodec/mpv_reconstruct_mb_template.c
@@ -173,7 +173,7 @@ void mpv_reconstruct_mb_internal(MpegEncContext *s, int16_t block[12][64],
             }
 
             /* add dct residue */
-            if (!(IS_MPEG12(s) || s->msmpeg4_version ||
+            if (!(IS_MPEG12(s) || s->msmpeg4_version != MSMP4_UNUSED ||
                   (s->codec_id == AV_CODEC_ID_MPEG4 && !s->mpeg_quant)))
 #endif /* !IS_ENCODER */
             {
diff --git a/libavcodec/msmpeg4.c b/libavcodec/msmpeg4.c
index f7ebb8ba89..50fd581a83 100644
--- a/libavcodec/msmpeg4.c
+++ b/libavcodec/msmpeg4.c
@@ -120,12 +120,12 @@ av_cold void ff_msmpeg4_common_init(MpegEncContext *s)
     static AVOnce init_static_once = AV_ONCE_INIT;
 
     switch(s->msmpeg4_version){
-    case 1:
-    case 2:
+    case MSMP4_V1:
+    case MSMP4_V2:
         s->y_dc_scale_table=
         s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
         break;
-    case 3:
+    case MSMP4_V3:
         if(s->workaround_bugs){
             s->y_dc_scale_table= ff_old_ff_y_dc_scale_table;
             s->c_dc_scale_table= ff_wmv1_c_dc_scale_table;
@@ -134,14 +134,14 @@ av_cold void ff_msmpeg4_common_init(MpegEncContext *s)
             s->c_dc_scale_table= ff_mpeg4_c_dc_scale_table;
         }
         break;
-    case 4:
-    case 5:
+    case MSMP4_WMV1:
+    case MSMP4_WMV2:
         s->y_dc_scale_table= ff_wmv1_y_dc_scale_table;
         s->c_dc_scale_table= ff_wmv1_c_dc_scale_table;
         break;
     }
 
-    if(s->msmpeg4_version>=4){
+    if (s->msmpeg4_version >= MSMP4_WMV1) {
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable,   ff_wmv1_scantable[1]);
         ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable,   ff_wmv1_scantable[0]);
         ff_permute_scantable(s->permutated_intra_h_scantable, ff_wmv1_scantable[2],
@@ -218,9 +218,8 @@ int ff_msmpeg4_pred_dc(MpegEncContext *s, int n,
     b = dc_val[ - 1 - wrap];
     c = dc_val[ - wrap];
 
-    if(s->first_slice_line && (n&2)==0 && s->msmpeg4_version<4){
+    if (s->first_slice_line && !(n & 2) && s->msmpeg4_version < MSMP4_WMV1)
         b=c=1024;
-    }
 
     /* XXX: the following solution consumes divisions, but it does not
        necessitate to modify mpegvideo.c. The problem comes from the
@@ -259,7 +258,7 @@ int ff_msmpeg4_pred_dc(MpegEncContext *s, int n,
 #endif
     /* XXX: WARNING: they did not choose the same test as MPEG-4. This
        is very important ! */
-    if(s->msmpeg4_version>3){
+    if (s->msmpeg4_version > MSMP4_V3) {
         if(s->inter_intra_pred){
             uint8_t *dest;
             int wrap;
diff --git a/libavcodec/msmpeg4dec.c b/libavcodec/msmpeg4dec.c
index 4143c46c15..209e1fe1b2 100644
--- a/libavcodec/msmpeg4dec.c
+++ b/libavcodec/msmpeg4dec.c
@@ -125,7 +125,7 @@ static int msmpeg4v12_decode_mb(MpegEncContext *s, int16_t block[6][64])
             }
         }
 
-        if(s->msmpeg4_version==2)
+        if (s->msmpeg4_version == MSMP4_V2)
             code = get_vlc2(&s->gb, v2_mb_type_vlc, V2_MB_TYPE_VLC_BITS, 1);
         else
             code = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc, INTER_MCBPC_VLC_BITS, 2);
@@ -139,7 +139,7 @@ static int msmpeg4v12_decode_mb(MpegEncContext *s, int16_t block[6][64])
         cbp = code & 0x3;
     } else {
         s->mb_intra = 1;
-        if(s->msmpeg4_version==2)
+        if (s->msmpeg4_version == MSMP4_V2)
             cbp = get_vlc2(&s->gb, v2_intra_cbpc_vlc, V2_INTRA_CBPC_VLC_BITS, 1);
         else
             cbp = get_vlc2(&s->gb, ff_h263_intra_MCBPC_vlc, INTRA_MCBPC_VLC_BITS, 2);
@@ -159,7 +159,8 @@ static int msmpeg4v12_decode_mb(MpegEncContext *s, int16_t block[6][64])
         }
 
         cbp|= cbpy<<2;
-        if(s->msmpeg4_version==1 || (cbp&3) != 3) cbp^= 0x3C;
+        if (s->msmpeg4_version == MSMP4_V1 || (cbp&3) != 3)
+            cbp ^= 0x3C;
 
         ff_h263_pred_motion(s, 0, 0, &mx, &my);
         mx= msmpeg4v2_decode_motion(s, mx, 1);
@@ -172,7 +173,7 @@ static int msmpeg4v12_decode_mb(MpegEncContext *s, int16_t block[6][64])
         *mb_type_ptr = MB_TYPE_L0 | MB_TYPE_16x16;
     } else {
         int v;
-        if(s->msmpeg4_version==2){
+        if (s->msmpeg4_version == MSMP4_V2) {
             s->ac_pred = get_bits1(&s->gb);
             v = get_vlc2(&s->gb, ff_h263_cbpy_vlc, CBPY_VLC_BITS, 1);
             if (v < 0) {
@@ -366,16 +367,16 @@ av_cold int ff_msmpeg4_decode_init(AVCodecContext *avctx)
 
     ff_msmpeg4_common_init(s);
 
-    switch(s->msmpeg4_version){
-    case 1:
-    case 2:
+    switch (s->msmpeg4_version) {
+    case MSMP4_V1:
+    case MSMP4_V2:
         s->decode_mb= msmpeg4v12_decode_mb;
         break;
-    case 3:
-    case 4:
+    case MSMP4_V3:
+    case MSMP4_WMV1:
         s->decode_mb= msmpeg4v34_decode_mb;
         break;
-    case 5:
+    case MSMP4_WMV2:
         break;
     }
 
@@ -398,7 +399,7 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
     if (get_bits_left(&s->gb) * 8LL < (s->width+15)/16 * ((s->height+15)/16))
         return AVERROR_INVALIDDATA;
 
-    if(s->msmpeg4_version==1){
+    if (s->msmpeg4_version == MSMP4_V1) {
         int start_code = get_bits_long(&s->gb, 32);
         if(start_code!=0x00000100){
             av_log(s->avctx, AV_LOG_ERROR, "invalid startcode\n");
@@ -422,7 +423,7 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
 
     if (s->pict_type == AV_PICTURE_TYPE_I) {
         code = get_bits(&s->gb, 5);
-        if(s->msmpeg4_version==1){
+        if (s->msmpeg4_version == MSMP4_V1) {
             if(code==0 || code>s->mb_height){
                 av_log(s->avctx, AV_LOG_ERROR, "invalid slice height %d\n", code);
                 return -1;
@@ -440,20 +441,20 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
         }
 
         switch(s->msmpeg4_version){
-        case 1:
-        case 2:
+        case MSMP4_V1:
+        case MSMP4_V2:
             s->rl_chroma_table_index = 2;
             s->rl_table_index = 2;
 
             s->dc_table_index = 0; //not used
             break;
-        case 3:
+        case MSMP4_V3:
             s->rl_chroma_table_index = decode012(&s->gb);
             s->rl_table_index = decode012(&s->gb);
 
             s->dc_table_index = get_bits1(&s->gb);
             break;
-        case 4:
+        case MSMP4_WMV1:
             ff_msmpeg4_decode_ext_header(s, (2+5+5+17+7)/8);
 
             if(s->bit_rate > MBAC_BITRATE) s->per_mb_rl_table= get_bits1(&s->gb);
@@ -479,9 +480,9 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
                 s->slice_height);
     } else {
         switch(s->msmpeg4_version){
-        case 1:
-        case 2:
-            if(s->msmpeg4_version==1)
+        case MSMP4_V1:
+        case MSMP4_V2:
+            if (s->msmpeg4_version == MSMP4_V1)
                 s->use_skip_mb_code = 1;
             else
                 s->use_skip_mb_code = get_bits1(&s->gb);
@@ -490,7 +491,7 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
             s->dc_table_index = 0; //not used
             s->mv_table_index = 0;
             break;
-        case 3:
+        case MSMP4_V3:
             s->use_skip_mb_code = get_bits1(&s->gb);
             s->rl_table_index = decode012(&s->gb);
             s->rl_chroma_table_index = s->rl_table_index;
@@ -499,7 +500,7 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
 
             s->mv_table_index = get_bits1(&s->gb);
             break;
-        case 4:
+        case MSMP4_WMV1:
             s->use_skip_mb_code = get_bits1(&s->gb);
 
             if(s->bit_rate > MBAC_BITRATE) s->per_mb_rl_table= get_bits1(&s->gb);
@@ -545,13 +546,13 @@ int ff_msmpeg4_decode_picture_header(MpegEncContext * s)
 int ff_msmpeg4_decode_ext_header(MpegEncContext * s, int buf_size)
 {
     int left= buf_size*8 - get_bits_count(&s->gb);
-    int length= s->msmpeg4_version>=3 ? 17 : 16;
+    int length = s->msmpeg4_version >= MSMP4_V3 ? 17 : 16;
     /* the alt_bitstream reader could read over the end so we need to check it */
     if(left>=length && left<length+8)
     {
         skip_bits(&s->gb, 5); /* fps */
         s->bit_rate= get_bits(&s->gb, 11)*1024;
-        if(s->msmpeg4_version>=3)
+        if (s->msmpeg4_version >= MSMP4_V3)
             s->flipflop_rounding= get_bits1(&s->gb);
         else
             s->flipflop_rounding= 0;
@@ -559,7 +560,7 @@ int ff_msmpeg4_decode_ext_header(MpegEncContext * s, int buf_size)
     else if(left<length+8)
     {
         s->flipflop_rounding= 0;
-        if(s->msmpeg4_version != 2)
+        if (s->msmpeg4_version != MSMP4_V2)
             av_log(s->avctx, AV_LOG_ERROR, "ext header missing, %d left\n", left);
     }
     else
@@ -574,7 +575,7 @@ static int msmpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr)
 {
     int level, pred;
 
-    if(s->msmpeg4_version<=2){
+    if (s->msmpeg4_version <= MSMP4_V2) {
         if (n < 4) {
             level = get_vlc2(&s->gb, v2_dc_lum_vlc, MSMP4_DC_VLC_BITS, 3);
         } else {
@@ -600,7 +601,7 @@ static int msmpeg4_decode_dc(MpegEncContext * s, int n, int *dir_ptr)
         }
     }
 
-    if(s->msmpeg4_version==1){
+    if (s->msmpeg4_version == MSMP4_V1) {
         int32_t *dc_val;
         pred = msmpeg4v1_pred_dc(s, n, &dc_val);
         level += pred;
@@ -658,7 +659,7 @@ int ff_msmpeg4_decode_block(MpegEncContext * s, int16_t * block,
         }
         block[0] = level;
 
-        run_diff = s->msmpeg4_version >= 4;
+        run_diff = s->msmpeg4_version >= MSMP4_WMV1;
         i = 0;
         if (!coded) {
             goto not_coded;
@@ -678,7 +679,7 @@ int ff_msmpeg4_decode_block(MpegEncContext * s, int16_t * block,
         i = -1;
         rl = &ff_rl_table[3 + s->rl_table_index];
 
-        if(s->msmpeg4_version==2)
+        if (s->msmpeg4_version == MSMP4_V2)
             run_diff = 0;
         else
             run_diff = 1;
@@ -700,12 +701,13 @@ int ff_msmpeg4_decode_block(MpegEncContext * s, int16_t * block,
             int cache;
             cache= GET_CACHE(re, &s->gb);
             /* escape */
-            if (s->msmpeg4_version==1 || (cache&0x80000000)==0) {
-                if (s->msmpeg4_version==1 || (cache&0x40000000)==0) {
+            if (s->msmpeg4_version == MSMP4_V1 || (cache&0x80000000)==0) {
+                if (s->msmpeg4_version == MSMP4_V1 || (cache&0x40000000)==0) {
                     /* third escape */
-                    if(s->msmpeg4_version!=1) LAST_SKIP_BITS(re, &s->gb, 2);
+                    if (s->msmpeg4_version != MSMP4_V1)
+                        LAST_SKIP_BITS(re, &s->gb, 2);
                     UPDATE_CACHE(re, &s->gb);
-                    if(s->msmpeg4_version<=3){
+                    if (s->msmpeg4_version <= MSMP4_V3) {
                         last=  SHOW_UBITS(re, &s->gb, 1); SKIP_CACHE(re, &s->gb, 1);
                         run=   SHOW_UBITS(re, &s->gb, 6); SKIP_CACHE(re, &s->gb, 6);
                         level= SHOW_SBITS(re, &s->gb, 8);
@@ -804,7 +806,7 @@ int ff_msmpeg4_decode_block(MpegEncContext * s, int16_t * block,
             i = 63; /* XXX: not optimal */
         }
     }
-    if(s->msmpeg4_version>=4 && i>0) i=63; //FIXME/XXX optimize
+    if (s->msmpeg4_version >= MSMP4_WMV1 && i > 0) i=63; //FIXME/XXX optimize
     s->block_last_index[n] = i;
 
     return 0;
diff --git a/libavcodec/msmpeg4enc.c b/libavcodec/msmpeg4enc.c
index 282b3e958b..a19d516947 100644
--- a/libavcodec/msmpeg4enc.c
+++ b/libavcodec/msmpeg4enc.c
@@ -141,7 +141,7 @@ av_cold void ff_msmpeg4_encode_init(MpegEncContext *s)
     static AVOnce init_static_once = AV_ONCE_INIT;
 
     ff_msmpeg4_common_init(s);
-    if (s->msmpeg4_version >= 4) {
+    if (s->msmpeg4_version >= MSMP4_WMV1) {
         s->min_qcoeff = -255;
         s->max_qcoeff =  255;
     }
@@ -226,7 +226,7 @@ void ff_msmpeg4_encode_picture_header(MpegEncContext * s)
     put_bits(&s->pb, 2, s->pict_type - 1);
 
     put_bits(&s->pb, 5, s->qscale);
-    if(s->msmpeg4_version<=2){
+    if (s->msmpeg4_version <= MSMP4_V2) {
         s->rl_table_index = 2;
         s->rl_chroma_table_index = 2;
     }
@@ -235,7 +235,7 @@ void ff_msmpeg4_encode_picture_header(MpegEncContext * s)
     s->mv_table_index = 1; /* only if P-frame */
     s->use_skip_mb_code = 1; /* only if P-frame */
     s->per_mb_rl_table = 0;
-    if(s->msmpeg4_version==4)
+    if (s->msmpeg4_version == MSMP4_WMV1)
         s->inter_intra_pred= (s->width*s->height < 320*240 && s->bit_rate<=II_BITRATE && s->pict_type==AV_PICTURE_TYPE_P);
     ff_dlog(s, "%d %"PRId64" %d %d %d\n", s->pict_type, s->bit_rate,
             s->inter_intra_pred, s->width, s->height);
@@ -244,13 +244,13 @@ void ff_msmpeg4_encode_picture_header(MpegEncContext * s)
         s->slice_height= s->mb_height/1;
         put_bits(&s->pb, 5, 0x16 + s->mb_height/s->slice_height);
 
-        if(s->msmpeg4_version==4){
+        if (s->msmpeg4_version == MSMP4_WMV1) {
             ff_msmpeg4_encode_ext_header(s);
             if(s->bit_rate>MBAC_BITRATE)
                 put_bits(&s->pb, 1, s->per_mb_rl_table);
         }
 
-        if(s->msmpeg4_version>2){
+        if (s->msmpeg4_version > MSMP4_V2) {
             if(!s->per_mb_rl_table){
                 ff_msmpeg4_code012(&s->pb, s->rl_chroma_table_index);
                 ff_msmpeg4_code012(&s->pb, s->rl_table_index);
@@ -261,10 +261,10 @@ void ff_msmpeg4_encode_picture_header(MpegEncContext * s)
     } else {
         put_bits(&s->pb, 1, s->use_skip_mb_code);
 
-        if(s->msmpeg4_version==4 && s->bit_rate>MBAC_BITRATE)
+        if (s->msmpeg4_version == MSMP4_WMV1 && s->bit_rate > MBAC_BITRATE)
             put_bits(&s->pb, 1, s->per_mb_rl_table);
 
-        if(s->msmpeg4_version>2){
+        if (s->msmpeg4_version > MSMP4_V2) {
             if(!s->per_mb_rl_table)
                 ff_msmpeg4_code012(&s->pb, s->rl_table_index);
 
@@ -298,7 +298,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
 
     put_bits(&s->pb, 11, FFMIN(s->bit_rate / 1024, 2047));
 
-    if (s->msmpeg4_version >= 3)
+    if (s->msmpeg4_version >= MSMP4_V3)
         put_bits(&s->pb, 1, s->flipflop_rounding);
     else
         av_assert0(!s->flipflop_rounding);
@@ -340,7 +340,7 @@ void ff_msmpeg4_encode_motion(MpegEncContext * s,
 void ff_msmpeg4_handle_slices(MpegEncContext *s){
     if (s->mb_x == 0) {
         if (s->slice_height && (s->mb_y % s->slice_height) == 0) {
-            if(s->msmpeg4_version < 4){
+            if (s->msmpeg4_version < MSMP4_WMV1) {
                 ff_mpeg4_clean_buffers(s);
             }
             s->first_slice_line = 1;
@@ -411,7 +411,7 @@ void ff_msmpeg4_encode_mb(MpegEncContext * s,
         if (s->use_skip_mb_code)
             put_bits(&s->pb, 1, 0);     /* mb coded */
 
-        if(s->msmpeg4_version<=2){
+        if (s->msmpeg4_version <= MSMP4_V2) {
             put_bits(&s->pb,
                      ff_v2_mb_type[cbp&3][1],
                      ff_v2_mb_type[cbp&3][0]);
@@ -453,7 +453,7 @@ void ff_msmpeg4_encode_mb(MpegEncContext * s,
             int val = (s->block_last_index[i] >= 1);
             cbp |= val << (5 - i);
         }
-        if(s->msmpeg4_version<=2){
+        if (s->msmpeg4_version <= MSMP4_V2) {
             if (s->pict_type == AV_PICTURE_TYPE_I) {
                 put_bits(&s->pb,
                          ff_v2_intra_cbpc[cbp&3][1], ff_v2_intra_cbpc[cbp&3][0]);
@@ -525,7 +525,7 @@ static void msmpeg4_encode_dc(MpegEncContext * s, int level, int n, int *dir_ptr
     /* do the prediction */
     level -= pred;
 
-    if(s->msmpeg4_version<=2){
+    if (s->msmpeg4_version <= MSMP4_V2) {
         if (n < 4) {
             put_bits(&s->pb,
                      ff_v2_dc_lum_table[level + 256][1],
@@ -576,20 +576,17 @@ void ff_msmpeg4_encode_block(MpegEncContext * s, int16_t * block, int n)
         } else {
             rl = &ff_rl_table[3 + s->rl_chroma_table_index];
         }
-        run_diff = s->msmpeg4_version>=4;
+        run_diff = s->msmpeg4_version >= MSMP4_WMV1;
         scantable= s->intra_scantable.permutated;
     } else {
         i = 0;
         rl = &ff_rl_table[3 + s->rl_table_index];
-        if(s->msmpeg4_version<=2)
-            run_diff = 0;
-        else
-            run_diff = 1;
+        run_diff = s->msmpeg4_version > MSMP4_V2;
         scantable= s->inter_scantable.permutated;
     }
 
     /* recalculate block_last_index for M$ wmv1 */
-    if (s->msmpeg4_version >= 4 && s->block_last_index[n] > 0) {
+    if (s->msmpeg4_version >= MSMP4_WMV1 && s->block_last_index[n] > 0) {
         for(last_index=63; last_index>=0; last_index--){
             if(block[scantable[last_index]]) break;
         }
@@ -635,7 +632,7 @@ void ff_msmpeg4_encode_block(MpegEncContext * s, int16_t * block, int n)
                     if (run1 < 0)
                         goto esc3;
                     code = get_rl_index(rl, last, run1+1, level);
-                    if (s->msmpeg4_version == 4 && code == rl->n)
+                    if (s->msmpeg4_version == MSMP4_WMV1 && code == rl->n)
                         goto esc3;
                     code = get_rl_index(rl, last, run1, level);
                     if (code == rl->n) {
@@ -643,7 +640,7 @@ void ff_msmpeg4_encode_block(MpegEncContext * s, int16_t * block, int n)
                         /* third escape */
                         put_bits(&s->pb, 1, 0);
                         put_bits(&s->pb, 1, last);
-                        if(s->msmpeg4_version>=4){
+                        if (s->msmpeg4_version >= MSMP4_WMV1) {
                             if(s->esc3_level_length==0){
                                 s->esc3_level_length=8;
                                 s->esc3_run_length= 6;
diff --git a/libavcodec/vc1dec.c b/libavcodec/vc1dec.c
index 0fac163c4f..906109e4a3 100644
--- a/libavcodec/vc1dec.c
+++ b/libavcodec/vc1dec.c
@@ -610,7 +610,7 @@ av_cold void ff_vc1_init_common(VC1Context *v)
     s->out_format      = FMT_H263;
 
     s->h263_pred       = 1;
-    s->msmpeg4_version = 6;
+    s->msmpeg4_version = MSMP4_VC1;
 
     ff_vc1dsp_init(&v->vc1dsp);
 
