Indeed MPEG1 should be supported, but remains mostly untested.
That patch should do the trick, I'll try to get it commited later if I manage to test it first.
http://cgit.freedesktop.org/~emericg/mesa-vp8/commit/?h=vp8&id=0c1f9a959bc42b51a2064922adca6d422273a79e

Mhm, Emeric you patch looks quite right to me.

But honestly, I couldn't find an MPEG1 to test it.Emeric you patch looks quite right to me.

But honestly, I couldn't find an MPEG1 to test it.

So could anybody please confirm that it's right so we can push it?

(In reply to comment #2)
> Mhm, Emeric you patch looks quite right to me.
> 
> But honestly, I couldn't find an MPEG1 to test it.Emeric you patch looks quite
> right to me.
> 
> But honestly, I couldn't find an MPEG1 to test it.
> 
> So could anybody please confirm that it's right so we can push it?

I have some MPEG1 videos, but I cannot test due to #39308 and #39309.

(In reply to comment #2)
> Mhm, Emeric you patch looks quite right to me.
> 
> But honestly, I couldn't find an MPEG1 to test it.Emeric you patch looks quite
> right to me.
> 
> But honestly, I couldn't find an MPEG1 to test it.

http://www.linux-video.net/Samples/Mpeg1/

> 
> So could anybody please confirm that it's right so we can push it?

Works OK for me on rv790 (OK meaning rendering with same issues as mpeg2), only tested the space shuttle vid from above.

Had to edit by hand as master seems to have changed somewhat - for reference here's the diff I tested with.

diff --git a/src/gallium/state_trackers/vdpau/decode.c b/src/gallium/state_trackers/vdpau/decode.c
index 269c7a4..931d62b 100644
--- a/src/gallium/state_trackers/vdpau/decode.c
+++ b/src/gallium/state_trackers/vdpau/decode.c
@@ -161,7 +161,7 @@ vlVdpDecoderGetParameters(VdpDecoder decoder,
 }
 
 static VdpStatus
-vlVdpDecoderRenderMpeg2(struct pipe_video_decoder *decoder,
+vlVdpDecoderRenderMpeg12(struct pipe_video_decoder *decoder,
                         struct pipe_video_decode_buffer *buffer,
                         struct pipe_video_buffer *target,
                         VdpPictureInfoMPEG1Or2 *picture_info,
@@ -256,11 +256,12 @@ vlVdpDecoderRender(VdpDecoder decoder,
 
    // TODO: Right now only mpeg2 is supported.
    switch (vldecoder->decoder->profile)   {
+   case PIPE_VIDEO_PROFILE_MPEG1:
    case PIPE_VIDEO_PROFILE_MPEG2_SIMPLE:
    case PIPE_VIDEO_PROFILE_MPEG2_MAIN:
       ++vldecoder->cur_buffer;
       vldecoder->cur_buffer %= VL_NUM_DECODE_BUFFERS;
-      return vlVdpDecoderRenderMpeg2(vldecoder->decoder,
+      return vlVdpDecoderRenderMpeg12(vldecoder->decoder,
                                      vldecoder->buffer[vldecoder->cur_buffer],
                                      vlsurf->video_buffer,
                                      (VdpPictureInfoMPEG1Or2 *)picture_info,

I can confirm that with this patch mpeg1 seems to work fine for most of the videos, but on some there are some major mc artefacts.

That doesn't happen with XvMC, so it seems to be a bug inside the bitstream decoder. It's a surprise that this works anyway, I just copied over the code from xine and have never tested it.

I pushed the patch anyway, so I think we can close the bug now.