+#define MAX_LEVEL 4
+typedef struct {
+ AVFormatContext *s;
+ AVIOContext pb;
+ Mp4Descr *descr;
+ Mp4Descr *active_descr;
+ int descr_count;
+ int max_descr_count;
+ int level;
+} MP4DescrParseContext;
+
+static int init_MP4DescrParseContext(
+ MP4DescrParseContext *d, AVFormatContext *s, const uint8_t *buf,
+ unsigned size, Mp4Descr *descr, int max_descr_count)
+{
+ int ret;
+ if (size > (1<<30))
+ return AVERROR_INVALIDDATA;
+
+ if ((ret = ffio_init_context(&d->pb, (unsigned char*)buf, size, 0,
+ NULL, NULL, NULL, NULL)) < 0)
+ return ret;
+
+ d->s = s;
+ d->level = 0;
+ d->descr_count = 0;
+ d->descr = descr;
+ d->active_descr = NULL;
+ d->max_descr_count = max_descr_count;
+
+ return 0;
+}
+
+static void update_offsets(AVIOContext *pb, int64_t *off, int *len) {
+ int64_t new_off = avio_tell(pb);
+ (*len) -= new_off - *off;
+ *off = new_off;
+}
+
+static int parse_mp4_descr(MP4DescrParseContext *d, int64_t off, int len,
+ int target_tag);
+
+static int parse_mp4_descr_arr(MP4DescrParseContext *d, int64_t off, int len)
+{
+ while (len > 0) {
+ if (parse_mp4_descr(d, off, len, 0) < 0)
+ return -1;
+ update_offsets(&d->pb, &off, &len);
+ }
+ return 0;
+}
+
+static int parse_MP4IODescrTag(MP4DescrParseContext *d, int64_t off, int len)
+{
+ avio_rb16(&d->pb); // ID
+ avio_r8(&d->pb);
+ avio_r8(&d->pb);
+ avio_r8(&d->pb);
+ avio_r8(&d->pb);
+ avio_r8(&d->pb);
+ update_offsets(&d->pb, &off, &len);
+ return parse_mp4_descr_arr(d, off, len);
+}
+
+static int parse_MP4ODescrTag(MP4DescrParseContext *d, int64_t off, int len)
+{
+ int id_flags;
+ if (len < 2)
+ return 0;
+ id_flags = avio_rb16(&d->pb);
+ if (!(id_flags & 0x0020)) { //URL_Flag
+ update_offsets(&d->pb, &off, &len);
+ return parse_mp4_descr_arr(d, off, len); //ES_Descriptor[]
+ } else {
+ return 0;
+ }
+}
+
+static int parse_MP4ESDescrTag(MP4DescrParseContext *d, int64_t off, int len)
+{
+ int es_id = 0;
+ if (d->descr_count >= d->max_descr_count)
+ return -1;
+ ff_mp4_parse_es_descr(&d->pb, &es_id);
+ d->active_descr = d->descr + (d->descr_count++);
+
+ d->active_descr->es_id = es_id;
+ update_offsets(&d->pb, &off, &len);
+ parse_mp4_descr(d, off, len, MP4DecConfigDescrTag);
+ update_offsets(&d->pb, &off, &len);
+ if (len > 0)
+ parse_mp4_descr(d, off, len, MP4SLDescrTag);
+ d->active_descr = NULL;
+ return 0;
+}
+
+static int parse_MP4DecConfigDescrTag(MP4DescrParseContext *d, int64_t off, int len)
+{
+ Mp4Descr *descr = d->active_descr;
+ if (!descr)
+ return -1;
+ d->active_descr->dec_config_descr = av_malloc(len);
+ if (!descr->dec_config_descr)
+ return AVERROR(ENOMEM);
+ descr->dec_config_descr_len = len;
+ avio_read(&d->pb, descr->dec_config_descr, len);
+ return 0;
+}
+
+static int parse_MP4SLDescrTag(MP4DescrParseContext *d, int64_t off, int len)
+{
+ Mp4Descr *descr = d->active_descr;
+ int predefined;
+ if (!descr)
+ return -1;
+
+ predefined = avio_r8(&d->pb);
+ if (!predefined) {
+ int lengths;
+ int flags = avio_r8(&d->pb);
+ descr->sl.use_au_start = !!(flags & 0x80);
+ descr->sl.use_au_end = !!(flags & 0x40);
+ descr->sl.use_rand_acc_pt = !!(flags & 0x20);
+ descr->sl.use_padding = !!(flags & 0x08);
+ descr->sl.use_timestamps = !!(flags & 0x04);
+ descr->sl.use_idle = !!(flags & 0x02);
+ descr->sl.timestamp_res = avio_rb32(&d->pb);
+ avio_rb32(&d->pb);
+ descr->sl.timestamp_len = avio_r8(&d->pb);
+ descr->sl.ocr_len = avio_r8(&d->pb);
+ descr->sl.au_len = avio_r8(&d->pb);
+ descr->sl.inst_bitrate_len = avio_r8(&d->pb);
+ lengths = avio_rb16(&d->pb);
+ descr->sl.degr_prior_len = lengths >> 12;
+ descr->sl.au_seq_num_len = (lengths >> 7) & 0x1f;
+ descr->sl.packet_seq_num_len = (lengths >> 2) & 0x1f;
+ } else {
+ av_log_missing_feature(d->s, "Predefined SLConfigDescriptor\n", 0);
+ }
+ return 0;
+}
+
+static int parse_mp4_descr(MP4DescrParseContext *d, int64_t off, int len,
+ int target_tag) {
+ int tag;
+ int len1 = ff_mp4_read_descr(d->s, &d->pb, &tag);
+ update_offsets(&d->pb, &off, &len);
+ if (len < 0 || len1 > len || len1 <= 0) {
+ av_log(d->s, AV_LOG_ERROR, "Tag %x length violation new length %d bytes remaining %d\n", tag, len1, len);
+ return -1;
+ }
+
+ if (d->level++ >= MAX_LEVEL) {
+ av_log(d->s, AV_LOG_ERROR, "Maximum MP4 descriptor level exceeded\n");
+ goto done;
+ }
+
+ if (target_tag && tag != target_tag) {
+ av_log(d->s, AV_LOG_ERROR, "Found tag %x expected %x\n", tag, target_tag);
+ goto done;
+ }
+
+ switch (tag) {
+ case MP4IODescrTag:
+ parse_MP4IODescrTag(d, off, len1);
+ break;
+ case MP4ODescrTag:
+ parse_MP4ODescrTag(d, off, len1);
+ break;
+ case MP4ESDescrTag:
+ parse_MP4ESDescrTag(d, off, len1);
+ break;
+ case MP4DecConfigDescrTag:
+ parse_MP4DecConfigDescrTag(d, off, len1);
+ break;
+ case MP4SLDescrTag:
+ parse_MP4SLDescrTag(d, off, len1);
+ break;
+ }
+
+done:
+ d->level--;
+ avio_seek(&d->pb, off + len1, SEEK_SET);
+ return 0;
+}
+