vpxenc: Move config check code into its own source files.

- Add command line args that allow display of warnings without prompting
  for user input.
- Extend warning code to make it somewhat scalable.

Change-Id: I2bad8f9315f6eed120c2e1bbe0a2a5ede15fbf35

warnings.c

diff --git a/warnings.c b/warnings.c
new file mode 100644
index 0000000..96400db
--- /dev/null
+++ b/warnings.c
@@ -0,0 +1,116 @@
+/*
+ *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "./warnings.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "vpx/vpx_encoder.h"
+
+#include "./tools_common.h"
+#include "./vpxenc.h"
+
+static const char quantizer_warning_string[] =
+    "Bad quantizer values. Quantizer values should not be equal, and should "
+    "differ by at least 8.";
+static const char lag_in_frames_with_realtime[] =
+    "Lag in frames is ignored when deadline is set to realtime.";
+
+struct WarningListNode {
+  const char *warning_string;
+  struct WarningListNode *next_warning;
+};
+
+struct WarningList {
+  struct WarningListNode *warning_node;
+};
+
+static void add_warning(const char *warning_string,
+                        struct WarningList *warning_list) {
+  struct WarningListNode **node = &warning_list->warning_node;
+
+  struct WarningListNode *new_node = malloc(sizeof(*new_node));
+  if (new_node == NULL) {
+    fatal("Unable to allocate warning node.");
+  }
+
+  new_node->warning_string = warning_string;
+  new_node->next_warning = NULL;
+
+  while (*node != NULL)
+    node = &(*node)->next_warning;
+
+  *node = new_node;
+}
+
+static void free_warning_list(struct WarningList *warning_list) {
+  struct WarningListNode *node = warning_list->warning_node;
+  while (warning_list->warning_node != NULL) {
+    node = warning_list->warning_node->next_warning;
+    free(warning_list->warning_node);
+    warning_list->warning_node = node;
+  }
+}
+
+static int continue_prompt(int num_warnings) {
+  int c;
+  fprintf(stderr,
+          "%d encoder configuration warning(s). Continue? (y to continue) ",
+          num_warnings);
+  c = getchar();
+  return c == 'y';
+}
+
+static void check_lag_in_frames_realtime_deadline(
+    int lag_in_frames,
+    int deadline,
+    struct WarningList *warning_list) {
+  if (deadline == VPX_DL_REALTIME && lag_in_frames != 0)
+    add_warning(lag_in_frames_with_realtime, warning_list);
+}
+
+static void check_quantizer(int min_q, int max_q,
+                            struct WarningList *warning_list) {
+  if (min_q == max_q || abs(max_q - min_q) < 8)
+    add_warning(quantizer_warning_string, warning_list);
+}
+
+void check_encoder_config(int disable_prompt,
+                          const struct VpxEncoderConfig *global_config,
+                          const struct vpx_codec_enc_cfg *stream_config) {
+  int num_warnings = 0;
+  struct WarningListNode *warning = NULL;
+  struct WarningList warning_list = {0};
+
+  check_quantizer(stream_config->rc_min_quantizer,
+                  stream_config->rc_max_quantizer,
+                  &warning_list);
+  check_lag_in_frames_realtime_deadline(stream_config->g_lag_in_frames,
+                                        global_config->deadline,
+                                        &warning_list);
+
+  /* Count and print warnings. */
+  for (warning = warning_list.warning_node;
+       warning != NULL;
+       warning = warning->next_warning,
+       ++num_warnings) {
+    warn(warning->warning_string);
+  }
+
+  free_warning_list(&warning_list);
+
+  if (num_warnings) {
+    if (!disable_prompt && !continue_prompt(num_warnings))
+      exit(EXIT_FAILURE);
+  }
+}