lavc: fix support of unofficial pix_fmt extensions of jpeg

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

libavcodec/utils.c

@@ -883,7 +883,9 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, AVCodec *codec, AVD
             for (i = 0; avctx->codec->pix_fmts[i] != PIX_FMT_NONE; i++)
                 if (avctx->pix_fmt == avctx->codec->pix_fmts[i])
                     break;
-            if (avctx->codec->pix_fmts[i] == PIX_FMT_NONE) {
+            if (avctx->codec->pix_fmts[i] == PIX_FMT_NONE
+                && !((avctx->codec_id == CODEC_ID_MJPEG || avctx->codec_id == CODEC_ID_LJPEG)
+                     && avctx->strict_std_compliance <= FF_COMPLIANCE_UNOFFICIAL)) {
                 av_log(avctx, AV_LOG_ERROR, "Specified pix_fmt is not supported\n");
                 ret = AVERROR(EINVAL);
                 goto free_and_end;