avcodec, avutil: allow more control about how samples are skipped

Add CODEC_FLAG2_SKIP_MANUAL (exposed as "skip_manual"), which makes
the decoder export sample skip information via side data, instead
of applying it automatically. The format of the side data is the
same as AV_PKT_DATA_SKIP_SAMPLES, but since AVPacket and AVFrame
side data constants overlap, AV_FRAME_DATA_SKIP_SAMPLES needs to
be introduced.

This is useful for applications which want to do the timestamp
calculations manually, or which actually want to retrieve the
padding.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/APIchanges

@@ -15,6 +15,13 @@ libavutil:     2014-08-09
 
 API changes, most recent first:
 
+2014-10-02 - xxxxxxx - lavc 56.2.100 - avcodec.h
+2014-10-02 - xxxxxxx - lavu 54.9.100 - frame.h
+  Add AV_FRAME_DATA_SKIP_SAMPLES. Add lavc CODEC_FLAG2_SKIP_MANUAL and
+  AVOption "skip_manual", which makes lavc export skip information via
+  AV_FRAME_DATA_SKIP_SAMPLES AVFrame side data, instead of skipping and
+  discarding samples automatically.
+
 2014-10-02 - xxxxxxx - lavu 54.8.100 - avstring.h
   Add av_match_list()
 

libavcodec/avcodec.h

@@ -768,6 +768,7 @@ typedef struct RcOverride{
 #define CODEC_FLAG2_CHUNKS        0x00008000 ///< Input bitstream might be truncated at a packet boundaries instead of only at frame boundaries.
 #define CODEC_FLAG2_SHOW_ALL      0x00400000 ///< Show all frames before the first keyframe
 #define CODEC_FLAG2_EXPORT_MVS    0x10000000 ///< Export motion vectors through frame side data
+#define CODEC_FLAG2_SKIP_MANUAL   0x20000000 ///< Do not skip samples and export skip information as frame side data
 
 /* Unsupported options :
  *              Syntax Arithmetic coding (SAC)

libavcodec/options_table.h

@@ -89,6 +89,7 @@ static const AVOption avcodec_options[] = {
 {"chunks", "Frame data might be split into multiple chunks", 0, AV_OPT_TYPE_CONST, {.i64 = CODEC_FLAG2_CHUNKS }, INT_MIN, INT_MAX, V|D, "flags2"},
 {"showall", "Show all frames before the first keyframe", 0, AV_OPT_TYPE_CONST, {.i64 = CODEC_FLAG2_SHOW_ALL }, INT_MIN, INT_MAX, V|D, "flags2"},
 {"export_mvs", "export motion vectors through frame side data", 0, AV_OPT_TYPE_CONST, {.i64 = CODEC_FLAG2_EXPORT_MVS}, INT_MIN, INT_MAX, V|D, "flags2"},
+{"skip_manual", "do not skip samples and export skip information as frame side data", 0, AV_OPT_TYPE_CONST, {.i64 = CODEC_FLAG2_SKIP_MANUAL}, INT_MIN, INT_MAX, V|D, "flags2"},
 {"me_method", "set motion estimation method", OFFSET(me_method), AV_OPT_TYPE_INT, {.i64 = ME_EPZS }, INT_MIN, INT_MAX, V|E, "me_method"},
 {"zero", "zero motion estimation (fastest)", 0, AV_OPT_TYPE_CONST, {.i64 = ME_ZERO }, INT_MIN, INT_MAX, V|E, "me_method" },
 {"full", "full motion estimation (slowest)", 0, AV_OPT_TYPE_CONST, {.i64 = ME_FULL }, INT_MIN, INT_MAX, V|E, "me_method" },

libavcodec/utils.c

@@ -2448,6 +2448,8 @@ int attribute_align_arg avcodec_decode_audio4(AVCodecContext *avctx,
         uint8_t *side;
         int side_size;
         uint32_t discard_padding = 0;
+        uint8_t skip_reason = 0;
+        uint8_t discard_reason = 0;
         // copy to ensure we do not change avpkt
         AVPacket tmp = *avpkt;
         int did_split = av_packet_split_side_data(&tmp);
@@ -2488,8 +2490,11 @@ int attribute_align_arg avcodec_decode_audio4(AVCodecContext *avctx,
             av_log(avctx, AV_LOG_DEBUG, "skip %d samples due to side data\n",
                    avctx->internal->skip_samples);
             discard_padding = AV_RL32(side + 4);
+            skip_reason = AV_RL8(side + 8);
+            discard_reason = AV_RL8(side + 9);
         }
-        if (avctx->internal->skip_samples && *got_frame_ptr) {
+        if (avctx->internal->skip_samples && *got_frame_ptr &&
+            !(avctx->flags2 & CODEC_FLAG2_SKIP_MANUAL)) {
             if(frame->nb_samples <= avctx->internal->skip_samples){
                 *got_frame_ptr = 0;
                 avctx->internal->skip_samples -= frame->nb_samples;
@@ -2518,7 +2523,8 @@ int attribute_align_arg avcodec_decode_audio4(AVCodecContext *avctx,
             }
         }
 
-        if (discard_padding > 0 && discard_padding <= frame->nb_samples && *got_frame_ptr) {
+        if (discard_padding > 0 && discard_padding <= frame->nb_samples && *got_frame_ptr &&
+            !(avctx->flags2 & CODEC_FLAG2_SKIP_MANUAL)) {
             if (discard_padding == frame->nb_samples) {
                 *got_frame_ptr = 0;
             } else {
@@ -2536,6 +2542,17 @@ int attribute_align_arg avcodec_decode_audio4(AVCodecContext *avctx,
                 frame->nb_samples -= discard_padding;
             }
         }
+
+        if ((avctx->flags2 & CODEC_FLAG2_SKIP_MANUAL) && *got_frame_ptr) {
+            AVFrameSideData *fside = av_frame_new_side_data(frame, AV_FRAME_DATA_SKIP_SAMPLES, 10);
+            if (fside) {
+                AV_WL32(fside->data, avctx->internal->skip_samples);
+                AV_WL32(fside->data + 4, discard_padding);
+                AV_WL8(fside->data + 8, skip_reason);
+                AV_WL8(fside->data + 9, discard_reason);
+                avctx->internal->skip_samples = 0;
+            }
+        }
 fail:
         avctx->internal->pkt = NULL;
         if (did_split) {

libavcodec/version.h

@@ -29,8 +29,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVCODEC_VERSION_MAJOR 56
-#define LIBAVCODEC_VERSION_MINOR  1
-#define LIBAVCODEC_VERSION_MICRO 102
+#define LIBAVCODEC_VERSION_MINOR  2
+#define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \

libavutil/frame.h

@@ -94,6 +94,18 @@ enum AVFrameSideDataType {
      * libavutil/motion_vector.h.
      */
     AV_FRAME_DATA_MOTION_VECTORS,
+    /**
+     * Recommmends skipping the specified number of samples. This is exported
+     * only if the "skip_manual" AVOption is set in libavcodec.
+     * This has the same format as AV_PKT_DATA_SKIP_SAMPLES.
+     * @code
+     * u32le number of samples to skip from start of this packet
+     * u32le number of samples to skip from end of this packet
+     * u8    reason for start skip
+     * u8    reason for end   skip (0=padding silence, 1=convergence)
+     * @endcode
+     */
+    AV_FRAME_DATA_SKIP_SAMPLES,
 };
 
 enum AVActiveFormatDescription {

libavutil/version.h

@@ -56,7 +56,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  54
-#define LIBAVUTIL_VERSION_MINOR   8
+#define LIBAVUTIL_VERSION_MINOR   9
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \