[FFmpeg-devel] [PATCH v5] Added Turing codec interface for ffmpeg
Saverio Blasi
Saverio.Blasi at bbc.co.uk
Fri Feb 10 17:48:55 EET 2017
> You probably shouldn't update options_buffer_size before the reallocation actually succeeded. (Probably doesn't matter with the current code, but for robustness...)
This is now addressed.
> Still not sure why there's at least 1 redundant field (s which is redundant with buffer_filled).
Truly s can be inferred from buffer_filled, but for readability and debugging purposes it is convenient to maintain both.s helps in keeping track of the current position within the options buffer.
> Not sure why this isn't just done by add_option.
This cannot be done inside add_option, because at the time of adding each option it is difficult to know how many options are passed to command line and consequently allocate argv
> Why do this extra check, instead of applying the internal values after the user options? (Assuming redundant options overwrite previous option values in libturing.)
While at the moment the behaviour of libturing is as you describe (overwriting redundant options with the last specified value) we would prefer to keep the interface transparent to this, in case we decide to change the behaviour of libturing in the future. We have slightly changed the log that is produced in case a redundant option is passed to clarify that the passed value is ignored.
> I think you should use av_mallocz to ensure the padding is cleared.
This is now done
-----Original Message-----
From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On Behalf Of wm4
Sent: 08 February 2017 09:28
To: ffmpeg-devel at ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH v5] Added Turing codec interface for ffmpeg
On Wed, 8 Feb 2017 08:41:56 +0000
Saverio Blasi <saverio.blasi at bbc.co.uk> wrote:
> - This patch contains the changes to interface the Turing codec (http://turingcodec.org/) with ffmpeg. The patch was modified to address the comments in the review as follows:
> - Added a pkg-config file to list all dependencies required by libturing. This should address the issue pointed out by Hendrik Leppkes on Fri 18/11/2016
> - As per suggestions of wm4, two functions (add_option and finalise_options) have been created. The former appends new options while the latter sets up the argv array of pointers to char* accordingly. add_option re-allocates the buffer for options using av_realloc
> - Additionally, both these functions handle the errors in case the memory wasn't allocated correctly
> - malloc|free|realloc have been substituted with their corresponding av_{malloc|free|realloc} version
> - Check on bit-depth has been removed since the ffmpeg already casts the right pix_fmt and bit depth
> - pix_fmts is now set in ff_libturing_encoder as in h264dec.c.
> - Added av_freep to release the allocated memory
> - Added brackets to single-line operators
> ---
> LICENSE.md | 1 +
> configure | 5 +
> libavcodec/Makefile | 1 +
> libavcodec/allcodecs.c | 1 +
> libavcodec/libturing.c | 320
> +++++++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 328 insertions(+)
> create mode 100644 libavcodec/libturing.c
The patch seems mostly ok, some minor comments below.
> +static av_cold int add_option(const char* current_option,
> +optionContext* option_ctx) {
> + int option_length = strlen(current_option);
> + char *temp_ptr;
> + if (option_ctx->buffer_filled + option_length + 1 > option_ctx->options_buffer_size) {
> + option_ctx->options_buffer_size += option_length + 1;
You probably shouldn't update options_buffer_size before the reallocation actually succeeded. (Probably doesn't matter with the current code, but for robustness...)
> + temp_ptr = av_realloc(option_ctx->options, option_ctx->options_buffer_size);
> + if (temp_ptr == NULL) {
> + return AVERROR(ENOMEM);
> + }
> + option_ctx->options = temp_ptr;
> + option_ctx->s = option_ctx->options + option_ctx->buffer_filled;
> + }
> + strcpy(option_ctx->s, current_option);
> + option_ctx->s += 1 + option_length;
> + option_ctx->options_added++;
> + option_ctx->buffer_filled += option_length + 1;
> + return 0;
> +}
Still not sure why there's at least 1 redundant field (s which is redundant with buffer_filled).
Using memcpy might be slightly nicer than strcpy, because everyone hates strcpy. But it looks correct anyway.
> +
> +static av_cold int finalise_options(optionContext* option_ctx) {
> + if (option_ctx->options_added) {
> + char *p;
> + option_ctx->argv = av_malloc(option_ctx->options_added * sizeof(char*));
> + if (option_ctx->argv == NULL) {
> + return AVERROR(ENOMEM);
> + }
> + p = option_ctx->options;
> + for(int option_idx=0; option_idx<option_ctx->options_added; option_idx++) {
> + option_ctx->argv[option_idx] = p;
> + p += strlen(p) + 1;
> + }
> + }
> + return 0;
> +}
Not sure why this isn't just done by add_option.
> +
> +static av_cold int libturing_encode_init(AVCodecContext *avctx) {
> + libturingEncodeContext *ctx = avctx->priv_data;
> + const int bit_depth =
> +av_pix_fmt_desc_get(avctx->pix_fmt)->comp[0].depth;
> +
> + optionContext encoder_options;
> + turing_encoder_settings settings;
> + char option_string[MAX_OPTION_LENGTH];
> + double frame_rate;
> +
> + frame_rate = (double)avctx->time_base.den / (avctx->time_base.num
> + * avctx->ticks_per_frame);
> +
> + encoder_options.buffer_filled = 0;
> + encoder_options.options_added = 0;
> + encoder_options.options_buffer_size = strlen("turing") + 1;
> + encoder_options.options = av_malloc(encoder_options.options_buffer_size);
> + if(encoder_options.options == NULL) {
> + av_log(avctx, AV_LOG_ERROR, "Cannot allocate the memory for command line options\n");
> + return AVERROR(ENOMEM);
> + }
Couldn't this extra initial allocation be dropped? It seems rather redundant.
> + encoder_options.s = encoder_options.options;
> + encoder_options.argv = NULL;
> +
> + // Add baseline command line options
> + if (add_option("turing", &encoder_options)) {
> + goto optionfail;
> + }
> +
> + if (add_option("--frames=0", &encoder_options)) {
> + goto optionfail;
> + }
> +
> + snprintf(option_string, MAX_OPTION_LENGTH, "--input-res=%dx%d", avctx->width, avctx->height);
> + if (add_option(option_string, &encoder_options)) {
> + goto optionfail;
> + }
Maybe add_option() could be a vararg function (like snprintf) to minimize this code further. Also, {/} are generally not considered necessary in this project if the body is just 1 line.
(You don't need to change this.)
> +
> + snprintf(option_string, MAX_OPTION_LENGTH, "--frame-rate=%f", frame_rate);
> + if (add_option(option_string, &encoder_options)) {
> + goto optionfail;
> + }
> +
> + snprintf(option_string, MAX_OPTION_LENGTH, "--bit-depth=%d", bit_depth);
> + if (add_option(option_string, &encoder_options)) {
> + goto optionfail;
> + }
> +
> + if (avctx->sample_aspect_ratio.num > 0 && avctx->sample_aspect_ratio.den > 0) {
> + int sar_num, sar_den;
> +
> + av_reduce(&sar_num, &sar_den,
> + avctx->sample_aspect_ratio.num,
> + avctx->sample_aspect_ratio.den, 65535);
> + snprintf(option_string, MAX_OPTION_LENGTH, "--sar=%d:%d", sar_num, sar_den);
> + if (add_option(option_string, &encoder_options)) {
> + goto optionfail;
> + }
> + }
> +
> + // Parse additional command line options
> + if (ctx->options) {
> + AVDictionary *dict = NULL;
> + AVDictionaryEntry *en = NULL;
> +
> + if (!av_dict_parse_string(&dict, ctx->options, "=", ":", 0)) {
> + while ((en = av_dict_get(dict, "", en, AV_DICT_IGNORE_SUFFIX))) {
> + int const illegal_option =
> + !strcmp("input-res", en->key) ||
> + !strcmp("frame-rate", en->key) ||
> + !strcmp("f", en->key) ||
> + !strcmp("frames", en->key) ||
> + !strcmp("sar", en->key) ||
> + !strcmp("bit-depth", en->key) ||
> + !strcmp("internal-bit-depth", en->key);
> + if (illegal_option) {
> + av_log(avctx, AV_LOG_WARNING, "%s=%s ignored.\n",
> + en->key, en->value);
Why do this extra check, instead of applying the internal values after the user options? (Assuming redundant options overwrite previous option values in libturing.)
> + } else {
> + if (turing_check_binary_option(en->key)) {
> + snprintf(option_string, MAX_OPTION_LENGTH, "--%s", en->key);
> + } else {
> + snprintf(option_string, MAX_OPTION_LENGTH, "--%s=%s", en->key, en->value);
> + }
> + if (add_option(option_string, &encoder_options)) {
> + goto optionfail;
> + }
> + }
> + }
> + av_dict_free(&dict);
> + }
> + }
> +
> + if (add_option("dummy-input-filename", &encoder_options)) {
> + goto optionfail;
> + }
> +
> + if (finalise_options(&encoder_options)) {
> + goto optionfail;
> + }
> +
> + settings.argv = (char const**)encoder_options.argv;
> + settings.argc = encoder_options.options_added;
> +
> + for (int i=0; i<settings.argc; ++i) {
> + av_log(avctx, AV_LOG_INFO, "arg %d: %s\n", i, settings.argv[i]);
> + }
> +
> + ctx->encoder = turing_create_encoder(settings);
> +
> + if (!ctx->encoder) {
> + av_log(avctx, AV_LOG_ERROR, "Failed to create libturing encoder.\n");
> + av_freep(&encoder_options.argv);
> + av_freep(&encoder_options.options);
> + return AVERROR_INVALIDDATA;
> + }
> +
> + if (avctx->flags & AV_CODEC_FLAG_GLOBAL_HEADER) {
> + turing_bitstream const *bitstream;
> + bitstream = turing_encode_headers(ctx->encoder);
> + if (bitstream->size <= 0) {
> + av_log(avctx, AV_LOG_ERROR, "Failed to encode headers.\n");
> + av_freep(&encoder_options.argv);
> + av_freep(&encoder_options.options);
> + turing_destroy_encoder(ctx->encoder);
> + return AVERROR_INVALIDDATA;
> + }
> +
> + avctx->extradata_size = bitstream->size;
> +
> + avctx->extradata = av_malloc(avctx->extradata_size +
> + AV_INPUT_BUFFER_PADDING_SIZE);
I think you should use av_mallocz to ensure the padding is cleared.
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