include/vlc_timestamp_helper.h

   1 /*****************************************************************************
   2  * vlc_timestamp_helper.h : timestamp handling helpers
   3  *****************************************************************************
   4  * Copyright (C) 2014 VLC authors and VideoLAN
   5  * $Id$
   6  *
   7  * Authors: Felix Abecassis <felix.abecassis@gmail.com>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU Lesser General Public License as published by
  11  * the Free Software Foundation; either version 2.1 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public License
  20  * along with this program; if not, write to the Free Software Foundation,
  21  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 #ifndef VLC_TIMESTAMP_H
  25 #define VLC_TIMESTAMP_H 1
  26
  27 /* Implementation of a circular buffer of timestamps with overwriting
  28  * of older values. MediaCodec has only one type of timestamp, if a
  29  * block has no PTS, we send the DTS instead. Some hardware decoders
  30  * cannot cope with this situation and output the frames in the wrong
  31  * order. As a workaround in this case, we use a FIFO of timestamps in
  32  * order to remember which input packets had no PTS.  Since an
  33  * hardware decoder can silently drop frames, this might cause a
  34  * growing desynchronization with the actual timestamp. Thus the
  35  * circular buffer has a limited size and will overwrite older values.
  36  */
  37 typedef struct
  38 {
  39     uint32_t          begin;
  40     uint32_t          size;
  41     uint32_t          capacity;
  42     int64_t           *buffer;
  43 } timestamp_fifo_t;
  44
  45 static inline timestamp_fifo_t *timestamp_FifoNew(uint32_t capacity)
  46 {
  47     timestamp_fifo_t *fifo = calloc(1, sizeof(*fifo));
  48     if (!fifo)
  49         return NULL;
  50     fifo->buffer = malloc(capacity * sizeof(*fifo->buffer));
  51     if (!fifo->buffer) {
  52         free(fifo);
  53         return NULL;
  54     }
  55     fifo->capacity = capacity;
  56     return fifo;
  57 }
  58
  59 static inline void timestamp_FifoRelease(timestamp_fifo_t *fifo)
  60 {
  61     free(fifo->buffer);
  62     free(fifo);
  63 }
  64
  65 static inline bool timestamp_FifoIsEmpty(timestamp_fifo_t *fifo)
  66 {
  67     return fifo->size == 0;
  68 }
  69
  70 static inline bool timestamp_FifoIsFull(timestamp_fifo_t *fifo)
  71 {
  72     return fifo->size == fifo->capacity;
  73 }
  74
  75 static inline void timestamp_FifoEmpty(timestamp_fifo_t *fifo)
  76 {
  77     fifo->size = 0;
  78 }
  79
  80 static inline void timestamp_FifoPut(timestamp_fifo_t *fifo, int64_t ts)
  81 {
  82     uint32_t end = (fifo->begin + fifo->size) % fifo->capacity;
  83     fifo->buffer[end] = ts;
  84     if (!timestamp_FifoIsFull(fifo))
  85         fifo->size += 1;
  86     else
  87         fifo->begin = (fifo->begin + 1) % fifo->capacity;
  88 }
  89
  90 static inline int64_t timestamp_FifoGet(timestamp_fifo_t *fifo)
  91 {
  92     if (timestamp_FifoIsEmpty(fifo))
  93         return VLC_TS_INVALID;
  94
  95     int64_t result = fifo->buffer[fifo->begin];
  96     fifo->begin = (fifo->begin + 1) % fifo->capacity;
  97     fifo->size -= 1;
  98     return result;
  99 }
 100
 101 #endif