The backwards scanning done for incomplete final packets should not assume a specific alignment at the end of the file. Truncated files result in hundreds of thousands of seeks if the final packet does not fall on a specific byte boundary, which can be extremely slow. For example, with HTTP, each backwards seek results in a separate HTTP request. This changes the scanning to check for the end tag 1 byte at a time and buffers the last 1 MiB to avoid additional seek operations.
Unified · Split
| @@ -22,6 +22,7 @@ · 21 unmodified lines | ||
| 22 | 22 | |
| 23 | 23 | #include <time.h> |
| 24 | 24 | |
| 25 | +#include "libavutil/intreadwrite.h" | |
| 25 | 26 | #include "libavutil/mem.h" |
| 26 | 27 | #include "libavutil/parseutils.h" |
| 27 | 28 | #include "avio_internal.h" |
| @@ -232,37 +233,60 @@ static void get_timeinfo(unsigned date, struct tm *timeinfo) · 204 unmodified lines | ||
| 232 | 233 | timeinfo->tm_sec = sec; |
| 233 | 234 | } |
| 234 | 235 | |
| 236 | +#define MAX_DURATION_BUFFER_SIZE (1024*1024) | |
| 237 | + | |
| 235 | 238 | static int64_t get_duration(AVFormatContext *s) |
| 236 | 239 | { |
| 237 | − DHAVContext *dhav = s->priv_data; | |
| 238 | 240 | int64_t start_pos = avio_tell(s->pb); |
| 241 | + int64_t end_pos = -1; | |
| 239 | 242 | int64_t start = 0, end = 0; |
| 240 | 243 | struct tm timeinfo; |
| 241 | − int max_interations = 100000; | |
| 244 | + uint8_t *end_buffer; | |
| 245 | + int64_t end_buffer_size; | |
| 246 | + int64_t end_buffer_pos; | |
| 247 | + int64_t offset; | |
| 248 | + unsigned date; | |
| 242 | 249 | |
| 243 | 250 | if (!s->pb->seekable) |
| 244 | 251 | return 0; |
| 245 | 252 | |
| 246 | − avio_seek(s->pb, avio_size(s->pb) - 8, SEEK_SET); | |
| 247 | − while (avio_tell(s->pb) > 12 && max_interations--) { | |
| 248 | − if (avio_rl32(s->pb) == MKTAG('d','h','a','v')) { | |
| 249 | − int64_t seek_back = avio_rl32(s->pb); | |
| 253 | + if (start_pos + 16 > avio_size(s->pb)) | |
| 254 | + return 0; | |
| 250 | 255 | |
| 251 | − avio_seek(s->pb, -seek_back, SEEK_CUR); | |
| 252 | − read_chunk(s); | |
| 253 | − get_timeinfo(dhav->date, &timeinfo); | |
| 254 | − end = av_timegm(&timeinfo) * 1000LL; | |
| 256 | + avio_skip(s->pb, 16); | |
| 257 | + date = avio_rl32(s->pb); | |
| 258 | + get_timeinfo(date, &timeinfo); | |
| 259 | + start = av_timegm(&timeinfo) * 1000LL; | |
| 260 | + | |
| 261 | + end_buffer_size = FFMIN(MAX_DURATION_BUFFER_SIZE, avio_size(s->pb)); | |
| 262 | + end_buffer = av_malloc(end_buffer_size); | |
| 263 | + if (!end_buffer) { | |
| 264 | + avio_seek(s->pb, start_pos, SEEK_SET); | |
| 265 | + return 0; | |
| 266 | + } | |
| 267 | + end_buffer_pos = avio_size(s->pb) - end_buffer_size; | |
| 268 | + avio_seek(s->pb, end_buffer_pos, SEEK_SET); | |
| 269 | + avio_read(s->pb, end_buffer, end_buffer_size); | |
| 270 | + | |
| 271 | + offset = end_buffer_size - 8; | |
| 272 | + while (offset > 0) { | |
| 273 | + if (AV_RL32(end_buffer + offset) == MKTAG('d','h','a','v')) { | |
| 274 | + int64_t seek_back = AV_RL32(end_buffer + offset + 4); | |
| 275 | + end_pos = end_buffer_pos + offset - seek_back + 8; | |
| 255 | 276 | break; |
| 256 | 277 | } else { |
| 257 | − avio_seek(s->pb, -12, SEEK_CUR); | |
| 278 | + offset -= 9; | |
| 258 | 279 | } |
| 259 | 280 | } |
| 260 | 281 | |
| 261 | − avio_seek(s->pb, start_pos, SEEK_SET); | |
| 282 | + if (end_pos < 0 || end_pos + 16 > end_buffer_pos + end_buffer_size) { | |
| 283 | + avio_seek(s->pb, start_pos, SEEK_SET); | |
| 284 | + return 0; | |
| 285 | + } | |
| 262 | 286 | |
| 263 | − read_chunk(s); | |
| 264 | − get_timeinfo(dhav->date, &timeinfo); | |
| 265 | − start = av_timegm(&timeinfo) * 1000LL; | |
| 287 | + date = AV_RL32(end_buffer + (end_pos - end_buffer_pos) + 16); | |
| 288 | + get_timeinfo(date, &timeinfo); | |
| 289 | + end = av_timegm(&timeinfo) * 1000LL; | |
| 266 | 290 | |
| 267 | 291 | avio_seek(s->pb, start_pos, SEEK_SET); |
| 268 | 292 | |