lavc: move bitstream filters into bsf/ subdir

libavcodec/bsf/mpeg4_unpack_bframes.c

@@ -0,0 +1,166 @@
+/*
+ * Bitstream filter for unpacking DivX-style packed B-frames in MPEG-4 (divx_packed)
+ * Copyright (c) 2015 Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "bsf.h"
+#include "bsf_internal.h"
+#include "mpeg4videodefs.h"
+#include "startcode.h"
+
+typedef struct UnpackBFramesBSFContext {
+    AVBufferRef *b_frame_ref;
+} UnpackBFramesBSFContext;
+
+/* determine the position of the packed marker in the userdata,
+ * the number of VOPs and the position of the second VOP */
+static void scan_buffer(const uint8_t *buf, int buf_size,
+                        int *pos_p, int *nb_vop, int *pos_vop2) {
+    uint32_t startcode;
+    const uint8_t *end = buf + buf_size, *pos = buf;
+
+    while (pos < end) {
+        startcode = -1;
+        pos = avpriv_find_start_code(pos, end, &startcode);
+
+        if (startcode == USER_DATA_STARTCODE && pos_p) {
+            /* check if the (DivX) userdata string ends with 'p' (packed) */
+            for (int i = 0; i < 255 && pos + i + 1 < end; i++) {
+                if (pos[i] == 'p' && pos[i + 1] == '\0') {
+                    *pos_p = pos + i - buf;
+                    break;
+                }
+            }
+        } else if (startcode == VOP_STARTCODE && nb_vop) {
+            *nb_vop += 1;
+            if (*nb_vop == 2 && pos_vop2) {
+                *pos_vop2 = pos - buf - 4; /* subtract 4 bytes startcode */
+            }
+        }
+    }
+}
+
+static int mpeg4_unpack_bframes_filter(AVBSFContext *ctx, AVPacket *pkt)
+{
+    UnpackBFramesBSFContext *s = ctx->priv_data;
+    int pos_p = -1, nb_vop = 0, pos_vop2 = -1, ret = 0;
+
+    ret = ff_bsf_get_packet_ref(ctx, pkt);
+    if (ret < 0)
+        return ret;
+
+    scan_buffer(pkt->data, pkt->size, &pos_p, &nb_vop, &pos_vop2);
+    av_log(ctx, AV_LOG_DEBUG, "Found %d VOP startcode(s) in this packet.\n", nb_vop);
+
+    if (pos_vop2 >= 0) {
+        if (s->b_frame_ref) {
+            av_log(ctx, AV_LOG_WARNING,
+                   "Missing one N-VOP packet, discarding one B-frame.\n");
+            av_buffer_unref(&s->b_frame_ref);
+        }
+        /* store a reference to the packed B-frame's data in the BSFContext */
+        s->b_frame_ref = av_buffer_ref(pkt->buf);
+        if (!s->b_frame_ref) {
+            ret = AVERROR(ENOMEM);
+            goto fail;
+        }
+        s->b_frame_ref->data = pkt->data + pos_vop2;
+        s->b_frame_ref->size = pkt->size - pos_vop2;
+    }
+
+    if (nb_vop > 2) {
+        av_log(ctx, AV_LOG_WARNING,
+       "Found %d VOP headers in one packet, only unpacking one.\n", nb_vop);
+    }
+
+    if (nb_vop == 1 && s->b_frame_ref) {
+        AVBufferRef *tmp = pkt->buf;
+
+        /* make tmp accurately reflect the packet's data */
+        tmp->data = pkt->data;
+        tmp->size = pkt->size;
+
+        /* replace data in packet with stored data */
+        pkt->buf  = s->b_frame_ref;
+        pkt->data = s->b_frame_ref->data;
+        pkt->size = s->b_frame_ref->size;
+
+        /* store reference to data into BSFContext */
+        s->b_frame_ref = tmp;
+
+        if (s->b_frame_ref->size <= MAX_NVOP_SIZE) {
+            /* N-VOP - discard stored data */
+            av_log(ctx, AV_LOG_DEBUG, "Skipping N-VOP.\n");
+            av_buffer_unref(&s->b_frame_ref);
+        }
+    } else if (nb_vop >= 2) {
+        /* use first frame of the packet */
+        pkt->size = pos_vop2;
+    } else if (pos_p >= 0) {
+        ret = av_packet_make_writable(pkt);
+        if (ret < 0)
+            goto fail;
+        av_log(ctx, AV_LOG_DEBUG, "Updating DivX userdata (remove trailing 'p').\n");
+        /* remove 'p' (packed) from the end of the (DivX) userdata string */
+        pkt->data[pos_p] = '\0';
+    } else {
+        /* use packet as is */
+    }
+
+fail:
+    if (ret < 0)
+        av_packet_unref(pkt);
+
+    return ret;
+}
+
+static int mpeg4_unpack_bframes_init(AVBSFContext *ctx)
+{
+    if (ctx->par_in->extradata) {
+        int pos_p_ext = -1;
+        scan_buffer(ctx->par_in->extradata, ctx->par_in->extradata_size, &pos_p_ext, NULL, NULL);
+        if (pos_p_ext >= 0) {
+            av_log(ctx, AV_LOG_DEBUG,
+                   "Updating DivX userdata (remove trailing 'p') in extradata.\n");
+            ctx->par_out->extradata[pos_p_ext] = '\0';
+        }
+    }
+
+    return 0;
+}
+
+static void mpeg4_unpack_bframes_close_flush(AVBSFContext *bsfc)
+{
+    UnpackBFramesBSFContext *ctx = bsfc->priv_data;
+    av_buffer_unref(&ctx->b_frame_ref);
+}
+
+static const enum AVCodecID codec_ids[] = {
+    AV_CODEC_ID_MPEG4, AV_CODEC_ID_NONE,
+};
+
+const FFBitStreamFilter ff_mpeg4_unpack_bframes_bsf = {
+    .p.name         = "mpeg4_unpack_bframes",
+    .p.codec_ids    = codec_ids,
+    .priv_data_size = sizeof(UnpackBFramesBSFContext),
+    .init           = mpeg4_unpack_bframes_init,
+    .filter         = mpeg4_unpack_bframes_filter,
+    .flush          = mpeg4_unpack_bframes_close_flush,
+    .close          = mpeg4_unpack_bframes_close_flush,
+};