h261: Set 'still image mode off' in picture header

Ref H.261 recommendation section 4.2.1.3, setting the still image flag
to 1 disables still image mode. Some decoders require this in order to
decode the bitstream as normal video.

Fixes H.261 calls to Cisco E20.

Also, reserved (aka spare) bits should be set to 1 unless specified
otherwise.

Bug-Id: 872
CC: libav-stable@libav.org
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/h261enc.c

@@ -70,8 +70,8 @@ void ff_h261_encode_picture_header(MpegEncContext *s, int picture_number)
 
     put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
 
-    put_bits(&s->pb, 1, 0); /* still image mode */
-    put_bits(&s->pb, 1, 0); /* reserved */
+    put_bits(&s->pb, 1, 1); /* still image mode */
+    put_bits(&s->pb, 1, 1); /* reserved */
 
     put_bits(&s->pb, 1, 0); /* no PEI */
     if (format == 0)

tests/ref/vsynth/vsynth1-h261

-d3397557ad8a02d28cb5feeb0b51e5c8 *tests/data/fate/vsynth1-h261.avi
+34263080870c91c5e6c3c7dca799c50d *tests/data/fate/vsynth1-h261.avi
 707576 tests/data/fate/vsynth1-h261.avi
 716e83cb51afb1246bfaa80967df48ea *tests/data/fate/vsynth1-h261.out.rawvideo
 stddev:    9.11 PSNR: 28.93 MAXDIFF:  113 bytes:  7603200/  7603200

tests/ref/vsynth/vsynth2-h261

-b5187bd5be8b422ff220f297de90fbcb *tests/data/fate/vsynth2-h261.avi
+70e9342de71456cd6fbe9a771cceefd5 *tests/data/fate/vsynth2-h261.avi
 257928 tests/data/fate/vsynth2-h261.avi
 1a9bb0d52bd24cb62162c5e3c2aed317 *tests/data/fate/vsynth2-h261.out.rawvideo
 stddev:    7.21 PSNR: 30.97 MAXDIFF:   96 bytes:  7603200/  7603200