lavc: deprecate FF_MAX_B_FRAMES

We should not arbitrarily decide the maximum B-frame number for all
encoders supported by Libav, each encoder should be able to set its own
limits.

libavcodec/avcodec.h

@@ -630,7 +630,12 @@ typedef struct RcOverride{
     float quality_factor;
 } RcOverride;
 
+#if FF_API_MAX_BFRAMES
+/**
+ * @deprecated there is no libavcodec-wide limit on the number of B-frames
+ */
 #define FF_MAX_B_FRAMES 16
+#endif
 
 /* encoding support
    These flags can be passed in AVCodecContext.flags before initialization.

libavcodec/mpegvideo.h

@@ -65,6 +65,8 @@ enum OutputFormat {
 
 #define MAX_PICTURE_COUNT 32
 
+#define MAX_B_FRAMES 16
+
 #define ME_MAP_SIZE 64
 #define ME_MAP_SHIFT 3
 #define ME_MAP_MV_BITS 11

libavcodec/mpegvideo_enc.c

@@ -290,6 +290,10 @@ av_cold int ff_MPV_encode_init(AVCodecContext *avctx)
     s->avctx        = avctx;
     s->flags        = avctx->flags;
     s->flags2       = avctx->flags2;
+    if (avctx->max_b_frames > MAX_B_FRAMES) {
+        av_log(avctx, AV_LOG_ERROR, "Too many B-frames requested, maximum "
+               "is %d.\n", MAX_B_FRAMES);
+    }
     s->max_b_frames = avctx->max_b_frames;
     s->codec_id     = avctx->codec->id;
     s->strict_std_compliance = avctx->strict_std_compliance;
@@ -1021,7 +1025,7 @@ static int estimate_best_b_count(MpegEncContext *s)
 {
     AVCodec *codec    = avcodec_find_encoder(s->avctx->codec_id);
     AVCodecContext *c = avcodec_alloc_context3(NULL);
-    AVFrame input[FF_MAX_B_FRAMES + 2];
+    AVFrame input[MAX_B_FRAMES + 2];
     const int scale = s->avctx->brd_scale;
     int i, j, out_size, p_lambda, b_lambda, lambda2;
     int64_t best_rd  = INT64_MAX;

libavcodec/options_table.h

@@ -101,7 +101,7 @@ static const AVOption avcodec_options[] = {
 {"qmin", "minimum video quantizer scale (VBR)", OFFSET(qmin), AV_OPT_TYPE_INT, {.i64 = 2 }, -1, 69, V|E},
 {"qmax", "maximum video quantizer scale (VBR)", OFFSET(qmax), AV_OPT_TYPE_INT, {.i64 = 31 }, -1, 69, V|E},
 {"qdiff", "maximum difference between the quantizer scales (VBR)", OFFSET(max_qdiff), AV_OPT_TYPE_INT, {.i64 = 3 }, INT_MIN, INT_MAX, V|E},
-{"bf", "use 'frames' B frames", OFFSET(max_b_frames), AV_OPT_TYPE_INT, {.i64 = DEFAULT }, -1, FF_MAX_B_FRAMES, V|E},
+{"bf", "use 'frames' B frames", OFFSET(max_b_frames), AV_OPT_TYPE_INT, {.i64 = DEFAULT }, -1, INT_MAX, V|E},
 {"b_qfactor", "QP factor between P- and B-frames", OFFSET(b_quant_factor), AV_OPT_TYPE_FLOAT, {.dbl = 1.25 }, -FLT_MAX, FLT_MAX, V|E},
 {"rc_strategy", "ratecontrol method", OFFSET(rc_strategy), AV_OPT_TYPE_INT, {.i64 = DEFAULT }, INT_MIN, INT_MAX, V|E},
 {"b_strategy", "strategy to choose between I/P/B-frames", OFFSET(b_frame_strategy), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, V|E},

libavcodec/version.h

@@ -109,5 +109,8 @@
 #ifndef FF_API_MB_TYPE
 #define FF_API_MB_TYPE           (LIBAVCODEC_VERSION_MAJOR < 56)
 #endif
+#ifndef FF_API_MAX_BFRAMES
+#define FF_API_MAX_BFRAMES       (LIBAVCODEC_VERSION_MAJOR < 56)
+#endif
 
 #endif /* AVCODEC_VERSION_H */