huffyuvenc: add a non-deterministic option

Not actually used in huffyuvenc, but rather in setting the frame
threading.

Example for some files:
context=0:       851974   27226   1137281
context=1,ND=0:  471819   22604    972351
context=1,ND=1:  472875   22673    972582
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/frame_thread_encoder.c

@@ -142,8 +142,16 @@ 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) {
+        int warn = 0;
+        if (avctx->flags & CODEC_FLAG_PASS1)
+            warn = 1;
+        else if(avctx->context_model > 0) {
+            AVDictionaryEntry *t = av_dict_get(options, "non_deterministic",
+                                               NULL, AV_DICT_MATCH_CASE);
+            warn = !t || !t->value || !atoi(t->value) ? 1 : 0;
+        }
         // huffyuv does not support these with multiple frame threads currently
-        if (avctx->context_model > 0 || (avctx->flags & CODEC_FLAG_PASS1)) {
+        if (warn) {
             av_log(avctx, AV_LOG_WARNING,
                "Forcing thread count to 1 for huffyuv encoding with first pass or context 1\n");
             avctx->thread_count = 1;

libavcodec/huffyuv.h

@@ -52,6 +52,7 @@ typedef enum Predictor {
 } Predictor;
 
 typedef struct HYuvContext {
+    AVClass *class;
     AVCodecContext *avctx;
     Predictor predictor;
     GetBitContext gb;
@@ -88,6 +89,7 @@ typedef struct HYuvContext {
     HuffYUVDSPContext hdsp;
     HuffYUVEncDSPContext hencdsp;
     LLVidDSPContext llviddsp;
+    int non_determ; // non-deterministic, multi-threaded encoder allowed
 } HYuvContext;
 
 void ff_huffyuv_common_init(AVCodecContext *s);

libavcodec/huffyuvenc.c

@@ -34,6 +34,7 @@
 #include "huffyuvencdsp.h"
 #include "internal.h"
 #include "put_bits.h"
+#include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
 
 static inline void diff_bytes(HYuvContext *s, uint8_t *dst,
@@ -990,6 +991,27 @@ static av_cold int encode_end(AVCodecContext *avctx)
     return 0;
 }
 
+static const AVOption options[] = {
+    { "non_deterministic", "Allow multithreading for e.g. context=1 at the expense of determinism",
+      offsetof(HYuvContext, non_determ), AV_OPT_TYPE_INT, { .i64 = 1 },
+      0, 1, AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_ENCODING_PARAM },
+    { NULL },
+};
+
+static const AVClass normal_class = {
+    .class_name = "huffyuv",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+static const AVClass ff_class = {
+    .class_name = "ffvhuff",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 AVCodec ff_huffyuv_encoder = {
     .name           = "huffyuv",
     .long_name      = NULL_IF_CONFIG_SMALL("Huffyuv / HuffYUV"),
@@ -1000,6 +1022,7 @@ AVCodec ff_huffyuv_encoder = {
     .encode2        = encode_frame,
     .close          = encode_end,
     .capabilities   = CODEC_CAP_FRAME_THREADS | CODEC_CAP_INTRA_ONLY,
+    .priv_class     = &normal_class,
     .pix_fmts       = (const enum AVPixelFormat[]){
         AV_PIX_FMT_YUV422P, AV_PIX_FMT_RGB24,
         AV_PIX_FMT_RGB32, AV_PIX_FMT_NONE
@@ -1017,6 +1040,7 @@ AVCodec ff_ffvhuff_encoder = {
     .encode2        = encode_frame,
     .close          = encode_end,
     .capabilities   = CODEC_CAP_FRAME_THREADS | CODEC_CAP_INTRA_ONLY,
+    .priv_class     = &ff_class,
     .pix_fmts       = (const enum AVPixelFormat[]){
         AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV411P,
         AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV440P,