[FFmpeg-devel] [PATCH v3 1/2] avfilter/dnn/dnn_backend_tf: simplify the code with ff_hex_to_data

[Guo, Yejun]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> lance.lmwang at gmail.com
> Sent: 2021年4月28日 18:47
> To: ffmpeg-devel at ffmpeg.org
> Cc: Limin Wang <lance.lmwang at gmail.com>
> Subject: [FFmpeg-devel] [PATCH v3 1/2] avfilter/dnn/dnn_backend_tf:
> simplify the code with ff_hex_to_data
> 
> From: Limin Wang <lance.lmwang at gmail.com>
> 
> please use tools/python/tf_sess_config.py to get the sess_config after that.
> note the byte order of session config is in normal order.
> bump the MICRO version for the config change.
> 
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
>  libavfilter/dnn/dnn_backend_tf.c | 42 +++++++------------------------------
>  libavfilter/version.h            |  2 +-
>  tools/python/tf_sess_config.py   | 45
> ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 54 insertions(+), 35 deletions(-)
>  create mode 100644 tools/python/tf_sess_config.py
> 
> diff --git a/libavfilter/dnn/dnn_backend_tf.c
> b/libavfilter/dnn/dnn_backend_tf.c
> index fb799d2..076dd3d 100644
> --- a/libavfilter/dnn/dnn_backend_tf.c
> +++ b/libavfilter/dnn/dnn_backend_tf.c
> @@ -28,6 +28,7 @@
>  #include "dnn_backend_native_layer_conv2d.h"
>  #include "dnn_backend_native_layer_depth2space.h"
>  #include "libavformat/avio.h"
> +#include "libavformat/internal.h"
>  #include "libavutil/avassert.h"
>  #include "../internal.h"
>  #include "dnn_backend_native_layer_pad.h"
> @@ -206,53 +207,26 @@ static DNNReturnType load_tf_model(TFModel
> *tf_model, const char *model_filename
> 
>      // prepare the sess config data
>      if (tf_model->ctx.options.sess_config != NULL) {
> +        const char *config;
>          /*
>          tf_model->ctx.options.sess_config is hex to present the serialized
> proto
>          required by TF_SetConfig below, so we need to first generate the
> serialized
> -        proto in a python script, the following is a script example to
> generate
> -        serialized proto which specifies one GPU, we can change the script
> to add
> -        more options.
> -
> -        import tensorflow as tf
> -        gpu_options = tf.GPUOptions(visible_device_list='0')
> -        config = tf.ConfigProto(gpu_options=gpu_options)
> -        s = config.SerializeToString()
> -        b = ''.join("%02x" % int(ord(b)) for b in s[::-1])
> -        print('0x%s' % b)
> -
> -        the script output looks like: 0xab...cd, and then pass 0xab...cd to
> sess_config.
> +        proto in a python script, tools/python/tf_sess_config.py is a script
> example
> +        to generate the configs of sess_config.
>          */
> -        char tmp[3];
> -        tmp[2] = '\0';
> -
>          if (strncmp(tf_model->ctx.options.sess_config, "0x", 2) != 0) {
>              av_log(ctx, AV_LOG_ERROR, "sess_config should start with
> '0x'\n");
>              return DNN_ERROR;
>          }
> +        config = tf_model->ctx.options.sess_config + 2;
> +        sess_config_length = ff_hex_to_data(NULL, config);
> 
> -        sess_config_length = strlen(tf_model->ctx.options.sess_config);
> -        if (sess_config_length % 2 != 0) {
> -            av_log(ctx, AV_LOG_ERROR, "the length of sess_config is not
> even (%s), "
> -                                      "please re-generate the
> config.\n",
> -
> tf_model->ctx.options.sess_config);
> -            return DNN_ERROR;
> -        }
> -
> -        sess_config_length -= 2; //ignore the first '0x'
> -        sess_config_length /= 2; //get the data length in byte
> -
> -        sess_config = av_malloc(sess_config_length);
> +        sess_config = av_mallocz(sess_config_length +
> AV_INPUT_BUFFER_PADDING_SIZE);

just get a concern, why we need to add PADDING_SIZE here.
Will there be potential issue if not add?

>          if (!sess_config) {
>              av_log(ctx, AV_LOG_ERROR, "failed to allocate memory\n");
>              return DNN_ERROR;
>          }
> -
> -        for (int i = 0; i < sess_config_length; i++) {
> -            int index = 2 + (sess_config_length - 1 - i) * 2;
> -            tmp[0] = tf_model->ctx.options.sess_config[index];
> -            tmp[1] = tf_model->ctx.options.sess_config[index + 1];
> -            sess_config[i] = strtol(tmp, NULL, 16);
> -        }
> +        ff_hex_to_data(sess_config, config);
>      }
>