include/vlc_timestamp_helper.h

   1 /*****************************************************************************
   2  * vlc_timestamp_helper.h : timestamp handling helpers
   3  *****************************************************************************
   4  * Copyright (C) 2014 VLC authors and VideoLAN
   5  *
   6  * Authors: Felix Abecassis <felix.abecassis@gmail.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU Lesser General Public License as published by
  10  * the Free Software Foundation; either version 2.1 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public License
  19  * along with this program; if not, write to the Free Software Foundation,
  20  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  21  *****************************************************************************/
  22
  23 #ifndef VLC_TIMESTAMP_H
  24 #define VLC_TIMESTAMP_H 1
  25
  26 /* Implementation of a circular buffer of timestamps with overwriting
  27  * of older values. MediaCodec has only one type of timestamp, if a
  28  * block has no PTS, we send the DTS instead. Some hardware decoders
  29  * cannot cope with this situation and output the frames in the wrong
  30  * order. As a workaround in this case, we use a FIFO of timestamps in
  31  * order to remember which input packets had no PTS.  Since an
  32  * hardware decoder can silently drop frames, this might cause a
  33  * growing desynchronization with the actual timestamp. Thus the
  34  * circular buffer has a limited size and will overwrite older values.
  35  */
  36 typedef struct
  37 {
  38     uint32_t          begin;
  39     uint32_t          size;
  40     uint32_t          capacity;
  41     vlc_tick_t        *buffer;
  42 } timestamp_fifo_t;
  43
  44 static inline timestamp_fifo_t *timestamp_FifoNew(uint32_t capacity)
  45 {
  46     timestamp_fifo_t *fifo = calloc(1, sizeof(*fifo));
  47     if (!fifo)
  48         return NULL;
  49     fifo->buffer = vlc_alloc(capacity, sizeof(*fifo->buffer));
  50     if (!fifo->buffer) {
  51         free(fifo);
  52         return NULL;
  53     }
  54     fifo->capacity = capacity;
  55     return fifo;
  56 }
  57
  58 static inline void timestamp_FifoRelease(timestamp_fifo_t *fifo)
  59 {
  60     free(fifo->buffer);
  61     free(fifo);
  62 }
  63
  64 static inline bool timestamp_FifoIsEmpty(timestamp_fifo_t *fifo)
  65 {
  66     return fifo->size == 0;
  67 }
  68
  69 static inline bool timestamp_FifoIsFull(timestamp_fifo_t *fifo)
  70 {
  71     return fifo->size == fifo->capacity;
  72 }
  73
  74 static inline void timestamp_FifoEmpty(timestamp_fifo_t *fifo)
  75 {
  76     fifo->size = 0;
  77 }
  78
  79 static inline void timestamp_FifoPut(timestamp_fifo_t *fifo, vlc_tick_t ts)
  80 {
  81     uint32_t end = (fifo->begin + fifo->size) % fifo->capacity;
  82     fifo->buffer[end] = ts;
  83     if (!timestamp_FifoIsFull(fifo))
  84         fifo->size += 1;
  85     else
  86         fifo->begin = (fifo->begin + 1) % fifo->capacity;
  87 }
  88
  89 static inline vlc_tick_t timestamp_FifoGet(timestamp_fifo_t *fifo)
  90 {
  91     if (timestamp_FifoIsEmpty(fifo))
  92         return VLC_TICK_INVALID;
  93
  94     vlc_tick_t result = fifo->buffer[fifo->begin];
  95     fifo->begin = (fifo->begin + 1) % fifo->capacity;
  96     fifo->size -= 1;
  97     return result;
  98 }
  99
 100 #endif