[FFmpeg-devel] [PATCH]lavc/mjpegenc: Add an option to force outputting chroma matrix

[Carl Eugen Hoyos]

Hi!

Attached patch adds an option to force writing chroma matrix even if it is 
identical to luma matrix as suggested by RFC 2435 for mjpeg over rtp.

Is force_write_chroma_matrix better?

Please comment, Carl Eugen
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diff --git a/libavcodec/mjpegenc_common.c b/libavcodec/mjpegenc_common.c
index d1d4cfb..7dadda8 100644
--- a/libavcodec/mjpegenc_common.c
+++ b/libavcodec/mjpegenc_common.c
@@ -64,11 +64,14 @@ static void jpeg_table_header(AVCodecContext *avctx, PutBitContext *p,
 {
     int i, j, size;
     uint8_t *ptr;
+    MpegEncContext *s = avctx->priv_data;
 
     if (avctx->codec_id != AV_CODEC_ID_LJPEG) {
         int matrix_count = 1 + !!memcmp(luma_intra_matrix,
                                         chroma_intra_matrix,
                                         sizeof(luma_intra_matrix[0]) * 64);
+    if (s->force_duplicated_matrix)
+        matrix_count = 2;
     /* quant matrixes */
     put_marker(p, DQT);
     put_bits(p, 16, 2 + matrix_count * (1 + 64));
diff --git a/libavcodec/mpegvideo.h b/libavcodec/mpegvideo.h
index 750388a..a2cd8e8 100644
--- a/libavcodec/mpegvideo.h
+++ b/libavcodec/mpegvideo.h
@@ -299,6 +299,7 @@ typedef struct MpegEncContext {
     uint16_t chroma_intra_matrix[64];
     uint16_t inter_matrix[64];
     uint16_t chroma_inter_matrix[64];
+    int force_duplicated_matrix; ///< Force duplication of mjpeg matrices, useful for rtp streaming
 
     int intra_quant_bias;    ///< bias for the quantizer
     int inter_quant_bias;    ///< bias for the quantizer
@@ -596,6 +597,7 @@ typedef struct MpegEncContext {
 { "zero", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = FF_ME_ZERO }, 0, 0, FF_MPV_OPT_FLAGS, "motion_est" }, \
 { "epzs", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = FF_ME_EPZS }, 0, 0, FF_MPV_OPT_FLAGS, "motion_est" }, \
 { "xone", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = FF_ME_XONE }, 0, 0, FF_MPV_OPT_FLAGS, "motion_est" }, \
+{ "force_duplicated_matrix", "Always write luma and chroma matrix for mjpeg, useful for rtp streaming.", FF_MPV_OFFSET(force_duplicated_matrix), AV_OPT_TYPE_BOOL, {.i64 = 0 }, 0, 1, FF_MPV_OPT_FLAGS },   \
 
 extern const AVOption ff_mpv_generic_options[];