What causes "%s: sorry, arithmetic coding not supported " in DrKLO/Telegram?

Drop the -arithmetic flag and use the default Huffman coding.

%s: sorry, arithmetic coding not supported

Error message

%s: sorry, arithmetic coding not supported

What it means

The -arithmetic flag was given to jpegtran but the encoder was built without C_ARITH_CODING_SUPPORTED. Arithmetic coding is a compile-time option in libjpeg/mozjpeg; when absent, the flag is rejected at parse time with exit(EXIT_FAILURE).

Source

Thrown at TMessagesProj/jni/mozjpeg/jpegtran.c:188

      /* Not a switch, must be a file name argument */
      if (argn <= last_file_arg_seen) {
        outfilename = NULL;     /* -outfile applies to just one input file */
        continue;               /* ignore this name if previously processed */
      }
      break;                    /* else done parsing switches */
    }
    arg++;                      /* advance past switch marker character */

    if (keymatch(arg, "arithmetic", 1)) {
      /* Use arithmetic coding. */
#ifdef C_ARITH_CODING_SUPPORTED
      cinfo->arith_code = TRUE;

      /* No table optimization required for AC */
      cinfo->optimize_coding = FALSE;
      prefer_smallest = FALSE;
#else
      fprintf(stderr, "%s: sorry, arithmetic coding not supported\n",
              progname);
      exit(EXIT_FAILURE);
#endif

    } else if (keymatch(arg, "copy", 2)) {
      /* Select which extra markers to copy. */
      if (++argn >= argc)       /* advance to next argument */
        usage();
      if (keymatch(argv[argn], "none", 1)) {
        copyoption = JCOPYOPT_NONE;
      } else if (keymatch(argv[argn], "comments", 1)) {
        copyoption = JCOPYOPT_COMMENTS;
      } else if (keymatch(argv[argn], "all", 1)) {
        copyoption = JCOPYOPT_ALL;
      } else
        usage();

    } else if (keymatch(arg, "crop", 2)) {

View on GitHub (pinned to 45ab8f4308)

Solutions

Drop the -arithmetic flag and use the default Huffman coding.
Rebuild libjpeg-turbo/mozjpeg with -DC_ARITH_CODING_SUPPORTED=1 (enable in CMake/Make config).
Verify the feature at build time: #ifdef C_ARITH_CODING_SUPPORTED in a probe before relying on it.
Document the build variant so callers know whether arithmetic coding is available.

Example fix

# before
./jpegtran -arithmetic in.jpg > out.jpg
# after: either drop the flag
./jpegtran in.jpg > out.jpg
# or rebuild: cmake -DCMAKE_C_FLAGS=-DC_ARITH_CODING_SUPPORTED=1 ...

Defensive patterns

Strategy: type-guard

Type guard

#ifndef C_ARITH_CODING_SUPPORTED
#error "arithmetic coding unavailable; do not pass -arithmetic"
#endif

Prevention

Guard -arithmetic usage behind a build-time feature probe.
Default to Huffman coding for portability across builds.
Rebuild with C_ARITH_CODING_SUPPORTED if arithmetic is required.

When it happens

Trigger: Passing -arithmetic (or -a) to a jpegtran that was compiled with arithmetic coding disabled. Common in distributions that ship only Huffman coding for licensing or size reasons.

Common situations: Default upstream libjpeg-turbo builds historically leave arithmetic coding enabled, but custom/minified builds or older libjpeg releases omit it; copying a command from a tutorial onto such a build fails immediately.

Related errors

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/af3aded6b23351c2. Report an issue: GitHub.