DrKLO/Telegram · error

failed to create a mode\n

Error message

failed to create a mode\n

What it means

opus_custom_mode_create(rate, frame_size, NULL) returned NULL — Opus could not build a custom mode for the given sample rate and frame size. The custom mode is the prerequisite for both encoder and decoder creation, so nothing else can proceed.

Source

Thrown at TMessagesProj/jni/opus/celt/opus_custom_demo.c:76

#endif
   int count = 0;
   opus_int32 skip;
   opus_int16 *in, *out;
   if (argc != 9 && argc != 8 && argc != 7)
   {
      fprintf (stderr, "Usage: test_opus_custom <rate> <channels> <frame size> "
               " <bytes per packet> [<complexity> [packet loss rate]] "
               "<input> <output>\n");
      return 1;
   }

   rate = (opus_int32)atol(argv[1]);
   channels = atoi(argv[2]);
   frame_size = atoi(argv[3]);
   mode = opus_custom_mode_create(rate, frame_size, NULL);
   if (mode == NULL)
   {
      fprintf(stderr, "failed to create a mode\n");
      return 1;
   }

   bytes_per_packet = atoi(argv[4]);
   if (bytes_per_packet < 0 || bytes_per_packet > MAX_PACKET)
   {
      fprintf (stderr, "bytes per packet must be between 0 and %d\n",
                        MAX_PACKET);
      return 1;
   }

   inFile = argv[argc-2];
   fin = fopen(inFile, "rb");
   if (!fin)
   {
      fprintf (stderr, "Could not open input file %s\n", argv[argc-2]);
      return 1;
   }

View on GitHub (pinned to 45ab8f4308)

Solutions

1. Use a rate/frame_size pair known valid for CELT custom mode (e.g. 48000 with frame_size in {120, 240, 480, 960, 1920, 2880}).
2. Check that the build defines CUSTOM_MODES; without it opus_custom_mode_create always returns NULL.
3. Validate argv values are positive integers before calling atol.
4. Inspect the error* out-param (here passed as NULL) — pass a non-NULL int* to get the specific OPUS_BAD_ARG / allocation code.

Example fix

// before
mode = opus_custom_mode_create(rate, frame_size, NULL);
if (mode == NULL) { fprintf(stderr, "failed to create a mode\n"); return 1; }

// after: capture the error code
int mode_err = 0;
mode = opus_custom_mode_create(rate, frame_size, &mode_err);
if (mode == NULL) { fprintf(stderr, "failed to create a mode: %s\n", opus_strerror(mode_err)); return 1; }

// Pass a real error out-param and validate rate/frame_size first.
if (rate <= 0 || frame_size <= 0) { fprintf(stderr, "rate and frame_size must be positive\n"); return 1; }
int mode_err = OPUS_OK;
mode = opus_custom_mode_create(rate, frame_size, &mode_err);
if (mode == NULL) { fprintf(stderr, "failed to create a mode: %s\n", opus_strerror(mode_err)); return 1; }

When it happens

Trigger: Passing an invalid rate or frame_size combination. opus_custom_mode_create requires specific constraints: rate typically 8000–48000, frame_size must fit the mode's internal CELT layout (e.g. multiples of the MDCT window / 2.5ms sub-frames), and the product must be representable. NULL is also returned on internal allocation failure.

Common situations: Using a frame size not supported by the custom CELT mode (e.g. non-multiple of 120 at 48kHz); an unsupported rate like 22050; passing 0 or negative values via atol on a malformed CLI arg; opus built without CUSTOM_MODES so the API rejects custom configs.

Related errors

• Failed to create the encoder: %s\n
• Failed to create the decoder: %s\n
• opus_custom_encode() failed: %s\n
• opus_custom_decode() failed: %s\n
• Error: encoder doesn't match decoder\n

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/a7517b5c592fa30b. Report an issue: GitHub.